FC for nonSSA Exec Mask manipulation instrs

[lalaniket8]

Functional changes for making wave transform non SSA compliant.

We create an accumulator to capture contributions from each thread level cfg parent, and accumulate the results into this register instead of creating a new register in the SSA variant of wave transform.
According to the reset semantic flags, the accumulator is reset to 0 at correct places.

[github-actions]

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