Implement liveliness support #1806

Job	Run time
Check c99 compilation	10s
Check codebase format with clang-format	7s
Test examples without router	9s
Build raweth transport on ubuntu-latest	39s
Run unit tests on ubuntu-latest	9s
Check compilation with unstable API	8s
Build Zenoh from source	5m 53s
Test multicast and unicast fragmentation	22s
Test attachments	19s
Test examples memory leak	38s
Modular build on ubuntu-latest (1, 1, 1, 1)	25s
Build and test in single thread on ubuntu-latest	18s
Modular build on ubuntu-latest (1, 1, 1, 0)	25s
Modular build on ubuntu-latest (1, 1, 0, 1)	15s
Modular build on ubuntu-latest (1, 1, 0, 0)	28s
Modular build on ubuntu-latest (1, 0, 1, 1)	26s
Modular build on ubuntu-latest (1, 0, 1, 0)	18s
Modular build on ubuntu-latest (1, 0, 0, 1)	18s
Modular build on ubuntu-latest (1, 0, 0, 0)	28s
Modular build on ubuntu-latest (0, 1, 1, 1)	15s
Modular build on ubuntu-latest (0, 1, 1, 0)	23s
Modular build on ubuntu-latest (0, 1, 0, 1)	14s
Modular build on ubuntu-latest (0, 1, 0, 0)	23s
Modular build on ubuntu-latest (0, 0, 1, 1)	14s
Modular build on ubuntu-latest (0, 0, 1, 0)	25s
Modular build on ubuntu-latest (0, 0, 0, 1)	14s
Modular build on ubuntu-latest (0, 0, 0, 0)	27s
	14m 30s

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