Improve config and files module

[isHarryh]

Summary

This PR makes code quality improvements to the files module, such as type hints and typo corrections.

Commit Details

1. fix: better type hint in EndianBinaryReader/Writer

In EndianBinaryReader, use -> Tuple[xxx, ...] instead of -> Tuple[xxx], where the latter one is a common mistake.

In EndianBinaryWriter, use value: Sequence instead of value: list because some invocations pass a tuple argument instead of list.

2. refactor(files): use assertion for version-specific assignment

Use assert xxx is not None before value assignment.

This is also the practice adopted by MeshHelper and other classes, which can correctly satisfy the NoneType checking.

3. chore(files): fix typo and remove legacy code

In File class:

• class File(object) can be simplified to class File (Python 3).
• self.environment = self.environment = ... causes a duplicated self-assignment.

In ContainerHelper, method __or__ cannot be used anymore since 5ac0a62 changed the constructor of this class.

4. fix(files): overall type hint corrections

Correct the type hints in the files module.

Refactors BundleFile.get_version_tuple:

• Uses (next(...), next(...), next(...)) instead of tuple(map(...)) to respect the returned type -> Tuple[int, int, int].
• Prevents AttributeError by validating the regex match before accessing groups.

Updates with 2 commits:

1. fix(files): use generic type in EndianBinaryWriter

Applies generic type to Sequence and Callable in EndianBinaryWriter.

2. feat(config): unset default fallback version

Sets the FALLBACK_UNITY_VERSION to None (unset).

Raises UnityVersionFallbackError when the fallback version is unset or invalid.

Refactors the warning mechanism using the warnings module.

Optimizes the documents string of the constants in the config.

[K0lb3]

Thanks for the PR.
I made most of these changes in the 1.21 files branch and the rewrite as well too.
As that branch is going to be shelved, I'm happy about your PR for fixing some of the hint and check issues of the current version.

[isHarryh]

Adds 2 commit:

1. fix(files): use generic type in EndianBinaryWriter

Applies generic type to Sequence and Callable in EndianBinaryWriter.

2. feat(config): unset default fallback version

Sets the FALLBACK_UNITY_VERSION to None (unset).

Raises UnityVersionFallbackError when the fallback version is unset or invalid.

Refactors the warning mechanism using the warnings module.

Optimizes the documents string of the constants in the config.

[K0lb3]

Thanks a lot 👍