Rename lib to `torrust_tracker_lib` #2117

Job	Run time
Formatting	22s
Build on ubuntu-latest (nightly)	3m 7s
Build on ubuntu-latest (stable)	3m 9s
Build on macos-latest (nightly)	3m 15s
Build on macos-latest (stable)	3m 0s
Build on windows-latest (nightly)	6m 3s
Build on windows-latest (stable)	7m 25s
Static Analysis (nightly)	2m 14s
Static Analysis (stable)	1m 53s
Units (nightly)	6m 23s
Units (stable)	6m 26s
E2E (nightly)	14m 19s
E2E (stable)	14m 14s
	1h 11m 50s

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