Use KnownBits to convert 64-bit sra to 32-bit sra.

Scaled-down alive2 verification with 16/8-bit types:
https://alive2.llvm.org/ce/z/LamASk

---------

Signed-off-by: John Lu <John.Lu@amd.com>

Should switch this to DiagnosticInfo and use the default calling
convention, but that would require passing in the context.

This was never constructed and only provided one static helper
function.

Convert vector 64-bit lshr to 32-bit if shift amt is known to be >= 32.
Also convert scalar 64-bit lshr to 32-bit if shift amt is variable but
known to be >=32.

---------

Signed-off-by: John Lu <John.Lu@amd.com>

Extend sra i64 simplification to shift constants in range [33:62]. Shift
amounts 32 and 63 were already handled.
New testing for shift amts 33 and 62 added in sra.ll. Changes to other
test files were to adapt previous test results to this extension.

---------

Signed-off-by: John Lu <John.Lu@amd.com>

This annotates the `Twine` passed to the constructors of the various
DiagnosticInfo subclasses with `[[clang::lifetimebound]]`, which causes
us to warn when we would try to print the twine after it had already
been destructed.

We also update `DiagnosticInfoUnsupported` to hold a `const Twine &`
like all of the other DiagnosticInfo classes, since this warning allows
us to clean up all of the places where it was being used incorrectly.

Introduces a slight regression in some cases but it'll even out once we
disable the promotion in CGP.

Update the f64 to f16 lowering for targets which support f16 types. 

For unsafe mode, lowered to two FP_ROUND. (This patch
https://reviews.llvm.org/D154528 stops from combining these two FP_ROUND
back). In safe mode, select LowerF64ToF16 (round-to-nearest-even
rounding mode)