Disassemble assemblable labels and determinize minification

[thaliaarchi]

To complement f7d1fe1 (Make binary label format (_010101) translate back from assembly to whitespace, so it round trips better, 2024-12-12), disassemble labels which match the pattern [a-zA-Z_][a-zA-Z0-9_]* as ASCII. That is, allow digits after the first character.

Secondly, assign minified labels deterministically. Prefer shorter labels for those more frequently used and break ties by order of label definition. Also, use big-endian order, e.g., 0, 1, 00, 01, 10, 11, 000, 001; instead of 0, 1, 00, 10, 01, 11, 000, 100.

[thaliaarchi]

As an illustration, this Whitespace assembly program has labels with the same usage count, so has a non-deterministic minification:

a: jmp a
b: jmp b
c: jmp c
d: jmp d
e: jmp e
f: jmp f
g: jmp g
h: jmp h
i: jmp i
j: jmp j

It would assemble to a non-deterministic permutation of this, subject to the seed of the HashMap:

_100:
    jmp   _100
_11:
    jmp   _11
_00:
    jmp   _00
_010:
    jmp   _010
_000:
    jmp   _000
_:
    jmp   _
_1:
    jmp   _1
_01:
    jmp   _01
_0:
    jmp   _0
_10:
    jmp   _10

With this change, it now always assembles to the following:

_:
    jmp   _
_0:
    jmp   _0
_1:
    jmp   _1
_00:
    jmp   _00
_01:
    jmp   _01
_10:
    jmp   _10
_11:
    jmp   _11
_000:
    jmp   _000
_001:
    jmp   _001
_010:
    jmp   _010