RFR: 8273349: Check uses of Stream::peek in controls and replace as needed

[drmarmac]

This PR removes potentially incorrect usages of Stream.peek().
The changed code should be covered by the tests that are already present.

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Commit messages:
 - Remove Stream.peek() operation

Changes: https://git.openjdk.org/jfx/pull/1430/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1430&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8273349
  Stats: 21 lines in 2 files changed: 10 ins; 1 del; 10 mod
  Patch: https://git.openjdk.org/jfx/pull/1430.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1430/head:pull/1430

PR: https://git.openjdk.org/jfx/pull/1430