Add search filter options for the Libraries tab in the Java Build Path dialog

The Libraries tab can list a lot of dependencies (usually in gradle/maven containers). It would be useful to be able to filter them when debugging buildpath issues. I suggest adding a free-text filter (could support regex is it's not too difficult) and filters for test-only only / non-tests-only entries.

These controls can be placed below the list like in the Source tab, or like in the Compiler > Errors/Warnings view on top.

Start in the Java Build Path dialog's Libraries tab and compare its existing controls with the Source tab and the Compiler > Errors/Warnings view. Determine how the list represents Gradle/Maven container dependencies and how test-only entries are identified. Done means the Libraries tab supports free-text filtering and separate test-only or non-test-only filtering while debugging build path issues.

Written by the indexing model from the issue text.