Introduce SingleByteCoverage tests (w/yaml2obj) (#113114)

Restructure some tests to split into `%.test` and Inputs/%.c*`.

Add test actions with `yaml2obj` for single byte coverage. `FileCheck`
l

Introduce SingleByteCoverage tests (w/yaml2obj) (#113114)

Restructure some tests to split into `%.test` and Inputs/%.c*`.

Add test actions with `yaml2obj` for single byte coverage. `FileCheck`
lines are:
- Relax to accept both counter values and single values `1`. A few line
counting are greater than `1` due to `llvm-profdata merge`. They will be
fixed by #110972.
- Suppress matching with `--check-prefixes=CHECK,BRCOV`, since the
current implementation of single byte doesn't emit any branch coverages.
They will be integrated to `CHECK` finally.
- Some tests are not unified but use dedicated `CHECK` lines for single
byte, since old format is different (esp. "partial fold"). They will be
unified when `Inputs` will be regenerated.

Introduce llvm/test/tools/llvm-cov/Inputs/yaml.makefile for convenience.
`%-single.yaml` and `%-single.proftext` are generated by it. It could be
used to regenerate other files.


https://discourse.llvm.org/t/rfc-integrating-singlebytecoverage-with-branch-coverage/82492

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