Semi-fix for bug #10013 (CSS Quick Edit provider does not respond if project
contians any non-UTF8 CSS/LESS/SCSS files) - Silently ignore files that can't
be read, and continue the search anyway (warning logged to console, but no
user-visible error shown). Similar to what we've always done for Find in Files.

With unit test, and matching test for the pre-existing same behavior in Find
in Files. Also clean up dated use of waitsFor() in the CSSUtils test spec.
Remove unused vars, fix typo in test suite name, leave error object
inspectable in console.warn() call.
Merge pull request #10052 from adobe/pflynn/cssinline-robust-fileio

Semi-fix bug #10013 (CSS Quick Edit provider does not respond if project contains any non-UTF8 CSS/LESS/SCSS files)