RFR: 4346610: Adding JSeparator to JToolBar "pushes" buttons added after separator to edge [v4]

[Prasanta Sadhukhan]

> Adding buttons in a JToolBar after a JSeparator will push the button to the far right of the frame instead of just after the separator
> 
> ![image](https://github.com/openjdk/jdk/assets/43534309/7fcad657-493f-4370-b046-b31c212a8aa7)
> 
> This is because BasicSeparatorUI does not define a maximum size. This leads to the separator getting all the extra width.
> Fix is made to limit the separator's maximum size to the preferred size of corresponding orientation (i.e. width for VERTICAL and height for HORIZONTAL)

Prasanta Sadhukhan has updated the pull request incrementally with one additional commit since the last revision:

  Test fix

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15054/files
  - new: https://git.openjdk.org/jdk/pull/15054/files/e023f6c6..bb46ee7c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15054&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15054&range=02-03

  Stats: 6 lines in 1 file changed: 0 ins; 4 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/15054.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15054/head:pull/15054

PR: https://git.openjdk.org/jdk/pull/15054