RFR: 8306083: Text.hitTest is incorrect when Text node is present in TextFlow [v4]

[Karthik P K]

> The text run selected in `PrismTextLayout::getHitInfo()` method for character index calculation was not correct when Text node was embedded in TextFlow. Hence wrong character index value was calculated for the same.
> 
> Since only x, y coordinates were available in the above mentioned method, sending the text as a parameter to this method is necessary so as to know if the text run selected for character index calculation is correct. Along with this change modified the `PrismTextLayout::getHitInfo()` method to calculate the correct character index.
> 
> Added tests to validate the changes.

Karthik P K has updated the pull request incrementally with one additional commit since the last revision:

  Fix character index calculation issue

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Changes:
  - all: https://git.openjdk.org/jfx/pull/1157/files
  - new: https://git.openjdk.org/jfx/pull/1157/files/c7eac8ab..1ea7365c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1157&range=03
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1157&range=02-03

  Stats: 22 lines in 1 file changed: 16 ins; 2 del; 4 mod
  Patch: https://git.openjdk.org/jfx/pull/1157.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1157/head:pull/1157

PR: https://git.openjdk.org/jfx/pull/1157