RFR: JDK-8297332: Remove easy warnings in base

[John Hendrikx]

- Remove unsupported/unnecessary SuppressWarning annotations
- Remove reduntant type specifications (use diamond operator)
- Remove unused or duplicate imports
- Remove unnecessary casts (type is already correct type or can be autoboxed)
- Remove unnecessary semi-colons (at end of class definitions, or just repeated ones)
- Remove redundant super interfaces (interface that is already inherited)
- Remove unused type parameters
- Remove declared checked exceptions that are never thrown
- Add missing `@Override` annotations

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Commit messages:
 - Fix easy warnings in base

Changes: https://git.openjdk.org/jfx/pull/957/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=957&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8297332
  Stats: 1269 lines in 265 files changed: 32 ins; 169 del; 1068 mod
  Patch: https://git.openjdk.org/jfx/pull/957.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/957/head:pull/957

PR: https://git.openjdk.org/jfx/pull/957