Fix resource by name lookup

Test: added: '@' cases to ResourceUtilsTest
      pass: ./out/host/darwin-x86/nativetest/libandroidfw_tests/libandroidfw_tests
      pass: ./out/host/darwin-x86/nativetest/aapt2_tests/aapt2_tests
      pass: cts-tradefed run cts-dev -m CtsAppSecurityHostTestCases
                -t android.appsecurity.cts.PermissionsHostTest

Bug: 74612500

Change-Id: I144e4ca1b63b9cce71052fc02089bb6092739889