feat: add perf walltime support #128

Job	Run time
tests	24s
cmake-integration-tests (instrumentation, ubuntu-latest)	1m 58s
bazel-integration-tests (walltime, codspeed-macro)	2m 29s
bazel-integration-tests (instrumentation, ubuntu-latest)	1m 15s
cmake-integration-tests (off, ubuntu-latest)	1m 9s
bazel-integration-tests (off, ubuntu-latest)	30s
cmake-integration-tests (walltime, codspeed-macro)	3m 38s
	11m 23s

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