RFR: 8370334: javadoc NPE with "import module" statement [v2]

[Jan Lahoda]

> `Modules.enter` completes all root modules, but in case of additional modules being added to the module graph via `Modules.addExtraAddModules` (either from javadoc, or using the `CompilationTask.addModules`, these extra modules may not be completed at this time. Normally, they are completed eventually, but if their `module-info`s contain `import module`, an NPE will appear while checking the import, before the complete happens.
> 
> The proposal herein is to consistently complete all modules in the module graph when the module graphs is setup.

Jan Lahoda has updated the pull request incrementally with one additional commit since the last revision:

  Don't eagerly complete the unnamed module.

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/27974/files
  - new: https://git.openjdk.org/jdk/pull/27974/files/ff2162ee..14ac910e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27974&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27974&range=00-01

  Stats: 4 lines in 1 file changed: 3 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/27974.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27974/head:pull/27974

PR: https://git.openjdk.org/jdk/pull/27974