Core: Unnecessary aria-describedby (#2410)

* Core: progress on removing aria-describedby from valid fields

* core: aria-describedby

* Core: remove aria-describedby when hiding error

* Core: fix syntax issues, Test: add test for new setting

* Core: Fix bugs in aria-describedby behavior and related tests

* Core: bugfix for labels without id

* Core: don't create a new error element if one exists

* Core: progress on test for group of fields with ariaDescribedbyCleanup

* Core: Groups aria-describedby

* Core: fix aria-describedby not being removed from grouped fields

Ensure that aria-describedby is removed from all members of a group when 
all the known errors are resolved

* Core: Update capitalization

* Demo: Add page for ariaDescribedByCleanup

* Core: add setting to remove aria-describedby from valid fields

Includes additional unit tests and a demo page

* Core: Fix camel case inconsistency, remove stray comment

* Update demo/css/cmxform.css

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

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Co-authored-by: Kieran <kieran.brahney@gmail.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>