compiler-rt: ubsan: Add suppressions test for nested functions (#206962)

This is a test-only change to increase the test coverage of UBSan to
clarify that named suppressions only apply to the function itself and do
not cover (possibly inlined) called functions.

The background is that, while trying to fix
https://github.com/llvm/llvm-project/issues/132533, I discovered missing
test coverage and possibly confused myself into a wrong fix in
https://github.com/llvm/llvm-project/pull/206735#discussion_r3505816693

So I think it could make sense to add test coverage for the case that I
broke, which serves as a reference baseline ground truth.

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Co-authored-by: MarcoFalke <*~=`'#}+{/-|&$^_@721217.xyz>
NOKEYCHECK=True
GitOrigin-RevId: 5db1f5442ef0c9bcb2f4ca362361daaf2a76acfb