Backport: Add !noalias and !alias.scope metadata
#48485
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The main idea here is that the TBAA domain is ill-equipped for reasoning about regions (and, in particular, suffers total precision less when merging disparate types in a `memcpy`). Instead, `!noalias` should be used for region-based memory information and `!tbaa` should be used exclusively for layout. We use (5) regions corresponding to the top level of the TBAA tree: - gcframe - stack - data - constant - type_metadata For now, this leaves the TBAA hierarchy in tact and only adds additional `!noalias` metadata. `!tbaa` annotations should be the same as before.
This is an interim solution that derives the correct `!noalias`
region from the existing TBAA information.
Later we will want to:
- Revise the TBAA hierarchy to remove region information
- Delete `jl_aliasinfo_t::fromTBAA()`
- Update `jl_cgval_t` to store a `jl_aliasinfo_t`
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Backport of #48256, fixing a few merge conflicts