RFR: 8345398: Avoid redundant Properties.containsKey call in Cursor.getSystemCustomCursor [v2]

[Andrey Turbanov]

> `Properties` doesn't allow `null` values.
> We can replace containsKey+getProperty with getProperty+null check.
> It's clearer and a bit faster.

Andrey Turbanov has updated the pull request incrementally with one additional commit since the last revision:

  inline 'key'
  remove 'final' from 'localized' too

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/21824/files
  - new: https://git.openjdk.org/jdk/pull/21824/files/36553550..5fcd5339

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21824&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21824&range=00-01

  Stats: 4 lines in 1 file changed: 1 ins; 1 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/21824.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21824/head:pull/21824

PR: https://git.openjdk.org/jdk/pull/21824