Hide `zenoh_config` internals #8595

Job	Run time
Typos Check	4s
Unit tests on ubuntu-latest	22m 38s
Lints and doc tests on ubuntu-latest	9m 13s
Unit tests on windows-latest	17m 10s
Lints and doc tests on windows-latest	12m 55s
Unit tests on macos-13	16m 4s
Lints and doc tests on macos-13	14m 56s
Unit tests on macos-14	11m 47s
Lints and doc tests on macos-14	7m 39s
Memory leak checks	2m 13s
CI status checks	1s
	1h 54m 40s

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