RFR: 8297437: javadoc cannot link to old docs (with old style anchors) [v2]

[Roman Marchenko]

> As it discussed on the mail list, checking presence of "element-list" or "package-list" is good enough approach to determine which type of anchors is used in external docs. The fix is for docs generated by 'supported' platforms only, i.e. 8, 11, ...
> 
> This fix extends `Extern.Item` with `useOldFormId` boolean flag to indicate a type of anchor. The boolean flag is set accordingly when reading a list of elements from either "element-list" or "package-list". 
> 
> Name transformation is performed in `Extern.getExternalLink()` by `getOldFormHtmlName()` call when creating `DocLink` instance.
> 
> Type of anchors used by platform docs are hard-coded in `isOldFormPlatformDocs()` (similar to `getPlatformElementList()`), since it's not supposed to rebuild platform docs on docs.oracle.com.

Roman Marchenko has updated the pull request incrementally with one additional commit since the last revision:

  Copyright changed, added the bug ID to TestLinkPlatform.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12066/files
  - new: https://git.openjdk.org/jdk/pull/12066/files/95d0ae76..224c5ef5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12066&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12066&range=00-01

  Stats: 7 lines in 6 files changed: 0 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/12066.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12066/head:pull/12066

PR: https://git.openjdk.org/jdk/pull/12066