Use Starlark tuples for C++ object-file groups

[dzbarsky]

Store private _ObjectFileGroupInfo.object_files collections as immutable Starlark tuples instead of Java-backed _cc_internal.freeze lists. Tuple iteration preserves object order, generated-directory expansion, and whole-archive grouping while removing the module's remaining cc_internal dependency.

Validation: buildifier -mode=check and 30 passing link-variable and Linux, macOS, and Windows toolchain-feature analysis tests.

[trybka]

@lberki can you take a quick look at this one? I know you added some of these freezes.
IIRC it was for mutability which the tuple should address, but just wanted to get another pair of 👀 .

[lilygorsheneva]

Ran some benchmarks on this and #809. Effects range from negligible to 0.05% increases in Post-Analysis JVM Heap Memory (nothing that should trip alerts).

[lberki]

From my POV, this works; all I care about is that these values are immutable, and a frozen list and a tuple both are good enough for the job. I guess lists fit the use case "philosophically" more, since the arity of a tuple is part of its type and with this change, you are effectively introducing a field whose type is a tuple of unknown arity.

That said, it's appealing to remove the cc_internal dependency. @pzembrod , which approach do you prefer?