feat: add perf walltime support #114

Job	Run time
tests	21s
cmake-integration-tests (off, ubuntu-latest)	12s
bazel-integration-tests (walltime, codspeed-macro)	1m 7s
cmake-integration-tests (walltime, codspeed-macro)	29s
cmake-integration-tests (instrumentation, ubuntu-latest)	11s
bazel-integration-tests (off, ubuntu-latest)	37s
bazel-integration-tests (instrumentation, ubuntu-latest)	1m 10s
	4m 7s

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