JIT: Reduce size of x86 intrinsic jump table fallbacks

[saucecontrol]

When generating jump table fallbacks for intrinsics that accept a control byte, we currently generate all 256 possible encodings for anything flagged HW_Flag_FullRangeIMM. Many of the corresponding instructions are documented to use a much smaller range of values, even though all values are allowed.

We can reduce the size of the generated fallback code significantly by masking or clamping the input byte and generating only useful instruction encodings.

Diffs:

Collection	Base size (bytes)	Diff size (bytes)	PerfScore in Diffs
benchmarks.run_pgo.windows.x64.checked.mch	35,255,449	-2,377	-90.60%
benchmarks.run_tiered.windows.x64.checked.mch	12,509,672	-2,377	-90.60%
coreclr_tests.run.windows.x64.checked.mch	409,037,918	-1,097,265	-94.46%
libraries.pmi.windows.x64.checked.mch	60,479,093	-551,918	-94.86%
libraries_tests.run.windows.x64.Release.mch	329,101,604	-2,377	-90.60%

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