Fix `custom-property-no-missing-var-function` false positives for recently introduced properties

Ref: https://github.com/stylelint/stylelint/pull/9466

Two related gaps are out of scope here because they belong to other specs: scroll-timeline-name / view-timeline-name (and their shorthands)

We often have to update this rule to manually add properties that accept <dashed-ident>s to the Set.

The same grammar is in the css-tree syntax data Stylelint already ships,

We could lessen the burden by using csstree's grammar:

IGNORED_PROPERTIES = Object.keys(lexer.properties).filter(p => !lexer.matchProperty(p, '--foo').error)

The change/refactor will fix the false positives for things like scroll-timeline-name, so we should classifying it as bug fix rather than a refactor.