Bugfix: swap="outerHTML" on <div> with style attribute leaves htmx-swapping class behind (#3341)

* Added regression test for swap=outerHTML unexpected behavior, checked it failes, implemented initial fix in htmx.js that makes (all) test(s) run and pass.

* Renamed variable in my regression test to be more clear.

* I noticed I wasn't using the copies of the attributes I introduced.Tests were passing and I know why, though. This means I miss one more regression test for the bug in cloneAttributes.

* Added one more regression test for the fix in cloneAttributes.

* Made preservation of htmx- prefixed classes more robust in cloneAttributes after I noted they could as well be removed by mergeTo.setAttribute in the second forEach loop.

* Started as a typo-fix, ended up renaming regression tests to be more explicit.

* Started as a typo-fix, ended up renaming regression tests to be more explicit.

* Removed space that I accidentally added before.

* Applied changes as requested by MichaelWest22.

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Co-authored-by: Matteo Smaila <matteo.smaila@314softwaresolutions.com>
Co-authored-by: 1cg <469183+1cg@users.noreply.github.com>