JIT: Reconsider block weight propagation in loop cloning

[amanasifkhalid]

Part of #93020. As mentioned in #102897, the logic in Compiler::optCloneLoops for propagating block weights is probably wrong when we have weights derived from PGO data -- in particular, we shouldn't need to scale weights based on the loop's depth. Doing so likely breaks block weight consistency (which we aren't checking just yet this late in the JIT's phases, hence the lack of assert failures).

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