RFR: 8264137: Suppress deprecation and removal warnings of internal methods

[Ajit Ghaisas]

This PR suppresses -PLINT="removal" warnings and fixes -PLINT="deprecation" warnings. I have created separate commits for each type of warnings for the ease of review.

`gradle --info -PLINT="deprecation,removal"` -- results in warnings during build without this PR and results in no warnings with this PR.

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Commit messages:
 - Fix LINT-deprecation warnings
 - Suppress LINT-removal warnings

Changes: https://git.openjdk.java.net/jfx/pull/538/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=538&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264137
  Stats: 111 lines in 9 files changed: 2 ins; 0 del; 109 mod
  Patch: https://git.openjdk.java.net/jfx/pull/538.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/538/head:pull/538

PR: https://git.openjdk.java.net/jfx/pull/538