RFR: 8272234: Pass originating elements from Filer to JavaFileManager [v7]

[Jan Lahoda]

> This is a first prototype of a patch that propagates originating elements from `Filer` (`createSourceFile`/`createClassFile`/`createResource`) to the corresponding methods in `JavaFileManager`. As file managers generally don't know about `Element`s, the `Element`s are first converted to their corresponding `FileObject`s (if any). As the currently existing methods only take one `FileObject` as a sibling of the newly created file, a new set of methods is proposed that take multiple originating files.
> 
> Any feedback on this prototype would be welcome.

Jan Lahoda has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 28 commits:

 - Merge branch 'master' into ap-keep-originating-elements
 - Applying changes as suggested on the review.
 - Improving javadoc as suggested in the PR.
 - Test cleanup.
 - Merge branch 'ap-keep-originating-elements' into ap-keep-originating-elements-forwarding-tweak
 - Cleanup
 - Merge branch 'master' into ap-keep-originating-elements
 - Fixing test (need to exclude a private method from the test).
 - Fixing typo, as per review comments.
 - Fixing javadoc.
 - ... and 18 more: https://git.openjdk.java.net/jdk/compare/040b2c52...e191d936

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Changes: https://git.openjdk.java.net/jdk/pull/5076/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5076&range=06
  Stats: 728 lines in 7 files changed: 718 ins; 1 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5076.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5076/head:pull/5076

PR: https://git.openjdk.java.net/jdk/pull/5076