RFR: 8272234: Pass originating elements from Filer to JavaFileManager [v6]

[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 incrementally with one additional commit since the last revision:

  Improving javadoc as suggested in the PR.

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5076/files
  - new: https://git.openjdk.java.net/jdk/pull/5076/files/da4781a9..7c11f10d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5076&range=05
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5076&range=04-05

  Stats: 6 lines in 1 file changed: 4 ins; 0 del; 2 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