RFR: 8240499: Enforce whitespace checking for additional source files

[Kevin Rushforth]

The `.jcheck/conf` file is configured to check the same set of files as the old HG jcheck, namely files with the
following extensions:

    .java, .c, .h, .cpp, .hpp

The Skara git jcheck allows us to evolve the rules for white space checking compatibly.

This PR adds the following additional file extensions to the list of source files that need to be kept whitespace-clean:

    .cc, .css, .frag, .fxml, .g4, .gradle, .groovy, .hlsl, .jsl, .m, .metal, .mm, .stg, .vert

For ease of review, I have done the initial push as 2 commits. The first modifies the `.jcheck/conf` file and
`tools/scripts/checkWhiteSpace` script to add the additional extensions. The second fixes the whitespace errors in the
(39) files among those with the newly added extensions.

-------------

Commit messages:
 - 8240499: Enforce whitespace checking for additional source files
 - 8240499: Enforce whitespace checking for additional source files

Changes: https://git.openjdk.java.net/jfx/pull/301/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=301&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8240499
  Stats: 148 lines in 41 files changed: 0 ins; 16 del; 132 mod
  Patch: https://git.openjdk.java.net/jfx/pull/301.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/301/head:pull/301

PR: https://git.openjdk.java.net/jfx/pull/301