feat: add perf walltime support #116

Job	Run time
cmake-integration-tests (off, ubuntu-latest)	17s
tests	28s
bazel-integration-tests (walltime, codspeed-macro)	1m 17s
bazel-integration-tests (instrumentation, ubuntu-latest)	1m 27s
cmake-integration-tests (instrumentation, ubuntu-latest)	11s
bazel-integration-tests (off, ubuntu-latest)	19s
cmake-integration-tests (walltime, codspeed-macro)	27s
	4m 26s

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