RFR: 8242548: Honor line spacing in Labeled reflow calculation

[John Hendrikx]

This is a solution for 8242548.  There was zero test coverage, so I added a few tests for this as well.

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Commit messages:
 - 8242548: Honor line spacing in Labeled reflow calculation

Changes: https://git.openjdk.java.net/jfx/pull/173/files
 Webrev: https://webrevs.openjdk.java.net/jfx/173/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8242548
  Stats: 44 lines in 4 files changed: 40 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jfx/pull/173.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/173/head:pull/173

PR: https://git.openjdk.java.net/jfx/pull/173