Sync to upstream/release/621

[vegorov-rbx]

What's changed?

• Support for new 'require by string' RFC with relative paths and aliases in now enabled in Luau REPL application

New Type Solver

• Fixed assertion failure on generic table keys ([expr] = value)
• Fixed an issue with type substitution traversing into the substituted parts during type instantiation
• Fixed crash in union simplification when that union contained uninhabited unions and other types inside
• Union types in binary type families like add<a | b, c> are expanded into add<a, c> | add<b, c> to handle
• Added handling for type family solving creating new type families
• Fixed a bug with normalization operation caching types with unsolved parts
• Tables with uninhabited properties are now simplified to never
• Fixed failures found by fuzzer

Native Code Generation

• Added support for shared code generation between multiple Luau VM instances
• Fixed issue in load-store propagation and new tagged LOAD_TVALUE instructions
• Fixed issues with partial register dead store elimination causing failures in GC assists

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Internal Contributors

Co-authored-by: Aaron Weiss [email protected]
Co-authored-by: Alexander McCord [email protected]
Co-authored-by: Andy Friesen [email protected]
Co-authored-by: James McNellis [email protected]
Co-authored-by: Vighnesh Vijay [email protected]
Co-authored-by: Vyacheslav Egorov [email protected]