feat: add perf walltime support #146

Job	Run time
tests	27s
cmake-integration-tests (walltime, codspeed-macro)	3m 36s
bazel-integration-tests (instrumentation, ubuntu-latest)	1m 19s
windows-bazel-build (walltime)	1m 9s
cmake-integration-tests (off, ubuntu-latest)	1m 7s
cmake-integration-tests (instrumentation, ubuntu-latest)	2m 2s
windows-cmake-build (walltime)	59s
windows-bazel-build (off)	1m 14s
windows-cmake-build (off)	55s
bazel-integration-tests (walltime, codspeed-macro)	2m 26s
bazel-integration-tests (off, ubuntu-latest)	26s
	15m 40s

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