fix: MemoryCatalog to return absolute NamespaceIdents #6093

Job	Run time
Unit Tests (default)	5m 40s
Verify MSRV	3m 12s
Unit Tests (doc)	1m 50s
build_with_no_default_features (macos-latest)	54s
build_with_no_default_features (windows-latest)	1m 27s
build_with_no_default_features (ubuntu-latest)	32s
build (windows-latest)	5m 29s
build (ubuntu-latest)	3m 9s
build (macos-latest)	3m 45s
check (ubuntu-latest)	6m 11s
check (macos-latest)	7m 29s
	39m 38s

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