feat: add perf walltime support #145

Job	Run time
windows-cmake-build (walltime)	47s
tests	21s
bazel-integration-tests (walltime, codspeed-macro)	2m 28s
bazel-integration-tests (off, ubuntu-latest)	32s
bazel-integration-tests (instrumentation, ubuntu-latest)	1m 5s
windows-cmake-build (off)	43s
windows-bazel-build (walltime)	1m 18s
cmake-integration-tests (instrumentation, ubuntu-latest)	2m 6s
cmake-integration-tests (walltime, codspeed-macro)	3m 20s
windows-bazel-build (off)	1m 21s
cmake-integration-tests (off, ubuntu-latest)	1m 9s
	15m 10s

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