Cranelift: add bitops simplification rules

[myunbin]

This PR consolidates the changes from the following earlier PRs into a single branch:

• [Cranelift] (x | z) & (y | z) => (x & y) | z (and its dual) #12730
• [Cranelift] (x|y) ^ (x|~y) => ~x #12732
• [Cranelift] (~x) & (~y) -> ~(x | y) and its dual #12734

Those PRs developed overlap and conflicts as more bitops rules were added to the same file. To make review and merging easier, this PR supersedes them and contains the combined, up-to-date version of the changes.

Supersedes #12730, #12732, #12734.

#12730 adds the following rule:

(x | z) & (y | z) => (x & y) | z

and its dual: (x & z) | (y & z) => (x | y) & z

#12732 adds the following rule:

(x | y) ^ (x | ~y) => ~x

#12734 adds the following rule:

(~x) & (~y) -> ~(x | y)

and its dual: (~x) | (~y) -> ~(x & y)

Apologies for the inconvenience.

cc @bongjunj

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[alexcrichton]

Thanks for this!