RFR: Show null restriction markers in javadoc. [v2]

[Jan Lahoda]

> Adds null markers inside generated javadoc like this:
> <img width="1144" height="528" alt="null-markers-javadoc" src="https://github.com/user-attachments/assets/b97736ff-f240-4c88-b874-32a8f7c8743c" />
> 
> Not sure if this is the ideal UI, and this is the best way to do implement it.
> 
> I didn't add tests yet, given the representation may change with experience.

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

  Adding a test.

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

Changes:
  - all: https://git.openjdk.org/valhalla/pull/2022/files
  - new: https://git.openjdk.org/valhalla/pull/2022/files/51351369..c3d87723

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=2022&range=01
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=2022&range=00-01

  Stats: 78 lines in 1 file changed: 78 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/valhalla/pull/2022.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/2022/head:pull/2022

PR: https://git.openjdk.org/valhalla/pull/2022