Disable mutations for a parts of source code

[ligurio]

It's a well-known practice for source code analyzers to suppress warnings for a part of source code (line or file).
It would be good to support such feature for Mull too. It would be helpful on regular mutation testing in a projects.

Related:

Clang-Tidy uses NOLINT, https://clang.llvm.org/extra/clang-tidy/#suppressing-undesired-diagnostics
PVS Studio, https://www.viva64.com/en/m/0032/
Dextool uses "NOMUT" to annotate source code lines.

[AlexDenisov]

Since Mull is working on a lower-level, I'm afraid we cannot use source-based annotations for that.
As a workaround, I can suggest using filters such as --include-path and --exclude-path. These include/exclude mutations for a file based on a regex.

[AlexDenisov]

Just a follow up: that is possible and we'll have it as soon I'm done with JIT migration.