feat: add perf walltime support #118

Job	Run time
tests	19s
cmake-integration-tests (off, ubuntu-latest)	1m 6s
cmake-integration-tests (walltime, codspeed-macro)	2m 6s
cmake-integration-tests (instrumentation, ubuntu-latest)	1m 21s
bazel-integration-tests (walltime, codspeed-macro)	1m 5s
bazel-integration-tests (instrumentation, ubuntu-latest)	1m 4s
bazel-integration-tests (off, ubuntu-latest)	14s
	7m 15s

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