feat: add coverage report generation with cargo-llvm-cov #3730

Job	Run time
spell check with typos	4s
docs-pr	3s
check license headers	5s
update-guest-locks	0s
code-checks / windows-checks	1m 54s
build-guests (release) / build-guests	1m 9s
code-checks / linux-checks	1m 15s
build-guests (debug) / build-guests	1m 26s
build-test	0s
run-examples	0s
fuzzing	0s
report-ci-status	3s
	5m 59s

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