JIT: build pred lists early, persist them throughout compilation

[AndyAyersMS]

Currently there's a lag between incorporation of profile data (which happens quite early and uses its own flow edge representation) and building pred lists, and pred lists are sometimes dropped and recomputed from scratch (#49030).

We should be building pred lists early on and using those for profile incorporation, and then keep the lists valid and persistent throughout compilation.

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Issue Details

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Currently there's a lag between incorporation of profile data (which happens quite early and uses its own flow edge representation) and building pred lists, and pred lists are sometimes dropped and recomputed from scratch (#49030).

We should be building pred lists early on and using those for profile incorporation, and then keep the lists valid and persistent throughout compilation.

Author:	AndyAyersMS
Assignees:	-
Labels:	area-CodeGen-coreclr, untriaged
Milestone:	-

[AndyAyersMS]

Note this will likely happen incrementally -- moving the point where pred lists are built earlier and earlier and gradually fixing up the impacted areas of the jit.

Related work:

• enable robust checking JIT: Refactor post phase checks #80194
• fix Loop opts should not be recomputing pred lists from scratch #49030 so pred lists stay around forever
• get rid of the "cheap preds" as the actual pred lists should suffice JIT: remove cheap preds #81562
• clean up various opt outs when pred lists are not valid (many PRs, below)
• fix places where pred lists are not properly maintained (JIT: update fgReplaceJumpTarget to maintain pred lists #81246)
• get rid of the explicit pred list building phase and create pred lists during initial flow graph build (during fgLinkBasicBlocks, say) JIT: build pred lists when we first build the flow graph #81524