[rw1nkler]

This PR adds support for use support in TIv2, and makes it operational with bytecode interpreter that relies on TIv1 data structures.

What's included:

• Resolution of use-bound constants, functions, structs, and type aliases, used directly or reached via ColonRef on a whole-module use subject, including nested module paths
• Spawning use-imported procs and proc aliases
• Constexpr propagation for use-imported constants, so they work as parametric defaults
• A fix for an IR-conversion crash on whole-module use of a module named std

Implementation details:

• Shared ImportData helpers (ResolveUseImportedTarget, GetUseImportedModuleInfo) let the typechecker and bytecode emitter resolve a use-bound name consistently
• ColonRef resolution now distinguishes a whole-module use subject from a use-bound value
• The parser binds a use-bound proc's bare name plus .config/.next/.init keys to the same entry. Since all four resolve to the same proc, the identifier's suffix is the only signal for which member was meant. This suffix lookup runs independently at typecheck time and at bytecode-emission time.

This PR also re-enables the use-syntax end-to-end DSLX tests that were previously disabled pending TIv2 support.

[magancarz]

I rebased changes onto the latest main and removed support for use and legacy procs.

[richmckeever]

There are places, such as MakeTypeCheckedNumberOrEnumValue in inference_table_utils.cc has a case for use which returns UnimplementedError. We should make those consider UseTreeEntry appropriately and add test cases. An AI search would be a good idea for that, since they don't have uniform search criteria.

[rw1nkler]

I have found a few more corner cases, for example around importing constant foo from module foo. I expanded the existing tests so the cover the discovered corner cases too.

@richmckeever PTAL

I also added one do-not-merge commit on top, because with the current state of this repository I cannot build this branch correctly without it. It should be dropped later on when proper fix for sv-lang import is provided.