Remove support for small octals

[dkorpel]

Implementation for dlang/DIPs#235 to identify breakage on buildkite. If the DIP goes through it will start as a deprecation first.

Revival of #8490

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Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + dmd#14599"

[dkorpel]

Errors on buildkite are:

ae:
net/irc/common.d(180,28): Error: octal literals `01` are no longer supported, use `std.conv.octal!"1"` instead
net/irc/common.d(181,28): Error: octal literals `02` are no longer supported, use `std.conv.octal!"2"` instead
net/irc/common.d(182,28): Error: octal literals `03` are no longer supported, use `std.conv.octal!"3"` instead
net/irc/common.d(183,28): Error: octal literals `04` are no longer supported, use `std.conv.octal!"4"` instead
net/irc/common.d(184,28): Error: octal literals `05` are no longer supported, use `std.conv.octal!"5"` instead
net/irc/server.d(584,34): Error: octal literals `05` are no longer supported, use `std.conv.octal!"5"` instead

vibe:
../../data/vibe/data/bson.d(1052,32): Error: octal literals `07` are no longer supported, use `std.conv.octal!"7"` instead

dwt:
org.eclipse.swt.gtk.linux.x86/src/org/eclipse/swt/internal/image/GIFFileFormat.d(344,53): Error: octal literals `01` are no longer supported, use `std.conv.octal!"1"` instead
org.eclipse.swt.gtk.linux.x86/src/org/eclipse/swt/internal/image/JPEGScanHeader.d(108,9): Error: octal literals `00` are no longer supported, use `std.conv.octal!"0"` instead

mir:
../.dub/packages/mir-algorithm-3.18.2/mir-algorithm/source/mir/series.d(47,20): Error: octal literals `01` are no longer supported, use `std.conv.octal!"1"` instead
../.dub/packages/mir-algorithm-3.18.2/mir-algorithm/source/mir/series.d(47,24): Error: octal literals `01` are no longer supported, use `std.conv.octal!"1"` instead
../.dub/packages/mir-algorithm-3.18.2/mir-algorithm/source/mir/series.d(48,20): Error: octal literals `03` are no longer supported, use `std.conv.octal!"3"` instead
../.dub/packages/mir-algorithm-3.18.2/mir-algorithm/source/mir/series.d(48,24): Error: octal literals `01` are no longer supported, use `std.conv.octal!"1"` instead
../.dub/packages/mir-algorithm-3.18.2/mir-algorithm/source/mir/series.d(49,20): Error: octal literals `04` are no longer supported, use `std.conv.octal!"4"` instead
../.dub/packages/mir-algorithm-3.18.2/mir-algorithm/source/mir/series.d(49,24): Error: octal literals `01` are no longer supported, use `std.conv.octal!"1"` instead
../.dub/packages/mir-algorithm-3.18.2/mir-algorithm/source/mir/series.d(55,20): Error: octal literals `01` are no longer supported, use `std.conv.octal!"1"` instead
../.dub/packages/mir-algorithm-3.18.2/mir-algorithm/source/mir/series.d(55,24): Error: octal literals `01` are no longer supported, use `std.conv.octal!"1"` instead
../.dub/packages/mir-algorithm-3.18.2/mir-algorithm/source/mir/series.d(56,20): Error: octal literals `02` are no longer supported, use `std.conv.octal!"2"` instead
../.dub/packages/mir-algorithm-3.18.2/mir-algorithm/source/mir/series.d(56,24): Error: octal literals `01` are no longer supported, use `std.conv.octal!"1"` instead
../.dub/packages/mir-algorithm-3.18.2/mir-algorithm/source/mir/series.d(57,20): Error: octal literals `05` are no longer supported, use `std.conv.octal!"5"` instead
../.dub/packages/mir-algorithm-3.18.2/mir-algorithm/source/mir/series.d(57,24): Error: octal literals `01` are no longer supported, use `std.conv.octal!"1"` instead
../.dub/packages/mir-algorithm-3.18.2/mir-algorithm/source/mir/series.d(75,31): Error: octal literals `03` are no longer supported, use `std.conv.octal!"3"` instead
../.dub/packages/mir-algorithm-3.18.2/mir-algorithm/source/mir/series.d(75,35): Error: octal literals `01` are no longer supported, use `std.conv.octal!"1"` instead
../.dub/packages/mir-algorithm-3.18.2/mir-algorithm/source/mir/series.d(76,35): Error: octal literals `03` are no longer supported, use `std.conv.octal!"3"` instead
../.dub/packages/mir-algorithm-3.18.2/mir-algorithm/source/mir/series.d(76,39): Error: octal literals `01` are no longer supported, use `std.conv.octal!"1"` instead
../.dub/packages/mir-algorithm-3.18.2/mir-algorithm/source/mir/series.d(127,20): Error: octal literals `01` are no longer supported, use `std.conv.octal!"1"` instead
../.dub/packages/mir-algorithm-3.18.2/mir-algorithm/source/mir/series.d(127,24): Error: octal literals `01` are no longer supported, use `std.conv.octal!"1"` instead
../.dub/packages/mir-algorithm-3.18.2/mir-algorithm/source/mir/series.d(128,20): Error: octal literals `02` are no longer supported, use `std.conv.octal!"2"` instead
../.dub/packages/mir-algorithm-3.18.2/mir-algorithm/source/mir/series.d(128,24): Error: octal literals `01` are no longer supported, use `std.conv.octal!"1"` instead

Undead:
src/undead/dateparse.d(275,9): Error: octal literals `00` are no longer supported, use `std.conv.octal!"0"` instead
src/undead/dateparse.d(275,9): Error: octal literals `00` are no longer supported, use `std.conv.octal!"0"` instead
src/undead/dateparse.d(275,9): Error: octal literals `00` are no longer supported, use `std.conv.octal!"0"` instead
src/undead/dateparse.d(275,9): Error: octal literals `00` are no longer supported, use `std.conv.octal!"0"` instead
src/undead/dateparse.d(275,9): Error: octal literals `00` are no longer supported, use `std.conv.octal!"0"` instead
src/undead/dateparse.d(275,9): Error: octal literals `00` are no longer supported, use `std.conv.octal!"0"` instead

Closing for now, may be revived if the DIP gets accepted