Replace svgSalamander with jsvg

[weisJ]

See #664

[rogerbj]

@weisJ Great work! Just tried the FlatLafDemo and if any ColorFilter has been set using FlatSVGIcon.setColorFilter() or FlatSVGIcon.ColorFilter.setMapper(), nothing happens with jsvg. This can be tested in the FlatLafDemo and in the Extras tab.

[rogerbj]

@weisJ I also ran into a problem in FlatSVGIcon.loadFromStream():

URI dummyUri = new URI( "inputStreamSVG", "/flatlaf-stream-" + streamNumber++, null );

It produces an "Invalid protocol: inputStreamSVG" error.

Except for this and my other report it works a lot better with randomly tested SVGs as opposed with SvgSalmander that fail with those.

[DevCharly]

@weisJ many thanks for the PR and for JSVG 👍
@rogerbj thanks for testing.

I've reviewed it and fixed in color filter and loading from input stream issues.
Have also simplified the code a little bit by replacing internal use of URI with URL.
(URI was used/required for svgSalamander)

Will test this PR and JSVG in some other projects in the next weeks...

[weisJ]

Note that I had originally not changed the cache to take URLs as keys due to this problem: https://errorprone.info/bugpattern/URLEqualsHashCode

[DevCharly]

Many thanks for this hint. Didn't know that. Changed the cache key from URL to String to avoid that.