Handle identifier collisions in codegen

[clickingbuttons]

Make an identifier string pool per-file to handle naming clashes. Give user fields and enums their function, field, and type identifiers. Then:

1. Give modules their identifiers
2. Give inner fields (like _tab: flatbufferz.Table) their identifiers
3. Give function parameters their identifiers
4. Give temporary variables their identifiers

This will allow removing _s from field names (like _tab) and temporaries. It will also allow consistently naming the first self: Self parameter.

[travisstaloch]

partially addressed in 0a7d9d4

this solution still appends underscores to getters. i was able to prevent a collision between the 'People' namespace and the 'Foo.People()' getter which resulted from https://github.com/travisstaloch/flatbufferz/blob/main/examples/test.fbs.

i know its not ideal to change the getter from 'People()' to 'People_()'. i would rather modify the namespace.

i'll leave this open until i can modify the namespace in a follow up.