Don't consider "unassociated" child content types while matching files

[iloveeclipse]

Fixes https://github.com/eclipse-platform/eclipse.platform/issues/1207

[github-actions[bot]]

Test Results

   579 files   -  57     579 suites   - 57   42m 34s :stopwatch: -11s  3 796 tests  - 149   3 762 :white_check_mark:  - 160   23 :zzz: ±0  11 :x: +11  11 994 runs   - 447  11 797 :white_check_mark:  - 480  164 :zzz: ±0  33 :x: +33 

For more details on these failures, see this check.

Results for commit 3cb14534. ± Comparison against base commit a8f5ea32.

This pull request removes 149 tests.

AllCompareTests org.eclipse.compare.tests.AsyncExecTests ‑ testCancelOnRequeue
AllCompareTests org.eclipse.compare.tests.AsyncExecTests ‑ testQueueAdd
AllCompareTests org.eclipse.compare.tests.AsyncExecTests ‑ testWorker
AllCompareTests org.eclipse.compare.tests.CompareFileRevisionEditorInputTest ‑ testPrepareCompareInputWithNonLocalResourceTypedElements
AllCompareTests org.eclipse.compare.tests.CompareUIPluginTest ‑ testFindContentViewerDescriptorForTextType_StreamAccessor
AllCompareTests org.eclipse.compare.tests.CompareUIPluginTest ‑ testFindContentViewerDescriptor_TextType_NotStreamAccessor
AllCompareTests org.eclipse.compare.tests.CompareUIPluginTest ‑ testFindContentViewerDescriptor_UnknownType
AllCompareTests org.eclipse.compare.tests.ContentMergeViewerTest ‑ testFFFX
AllCompareTests org.eclipse.compare.tests.ContentMergeViewerTest ‑ testFFTX
AllCompareTests org.eclipse.compare.tests.ContentMergeViewerTest ‑ testFFXF
…