[jdk8u-dev] RFR: 8129572: Cleanup usage of getResourceAsStream in jaxp

[Alex Kasko]

Please review a backport of a JAXP cleanup.

Original commit [17b47acf5b3d](https://hg.openjdk.java.net/jdk9/jdk9/jaxp/rev/17b47acf5b3d) in jdk9.

Commit [4ebbfc9](https://github.com/openjdk/jdk11u-dev/commit/4ebbfc918f558e73c05f471cfd3ab2b11dcf5a75) in jdk11u-dev.

This cleanup should allow to backport other JAXP changes (like [JDK-8163121](https://bugs.openjdk.java.net/browse/JDK-8163121)) easier.

All code changes apply cleanly (with reshuffled paths) except [LSSerializerTest.java](https://github.com/openjdk/jdk11u-dev/blob/4ebbfc918f558e73c05f471cfd3ab2b11dcf5a75/jaxp/test/javax/xml/jaxp/unittest/org/w3c/dom/ls/LSSerializerTest.java) that was excluded. LSSerializerTest.java is not present in 8u, it was added with JDK-8043084 (not public, jdk9 commit [29ba77ad2a87](https://hg.openjdk.java.net/jdk9/jdk9/jaxp/rev/29ba77ad2a87)).

Testing:

 - [x] jtreg:javax/xml/jaxp
 - [x] jck:api/javax_xml

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Commit messages:
 - 8129572: Cleanup usage of getResourceAsStream in jaxp

Changes: https://git.openjdk.java.net/jdk8u-dev/pull/4/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk8u-dev&pr=4&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8129572
  Stats: 239 lines in 13 files changed: 0 ins; 229 del; 10 mod
  Patch: https://git.openjdk.java.net/jdk8u-dev/pull/4.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk8u-dev pull/4/head:pull/4

PR: https://git.openjdk.java.net/jdk8u-dev/pull/4