feat: add perf walltime support #117

Job	Run time
cmake-integration-tests (instrumentation, ubuntu-latest)	14s
tests	20s
cmake-integration-tests (walltime, codspeed-macro)	32s
bazel-integration-tests (walltime, codspeed-macro)	1m 13s
cmake-integration-tests (off, ubuntu-latest)	15s
bazel-integration-tests (instrumentation, ubuntu-latest)	2m 12s
bazel-integration-tests (off, ubuntu-latest)	21s
	5m 7s

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