feat: Support placeholders in S2 components (#8692)
* readd placeholder support to S2 components
* progress
* adding tests
* fix combobox placeholder warning
* apply specific color to placeholders
* getting rid of unneeded warnings and adding missing placeholders
* fix tests
* review comments
* fix tests
* remove placeholder warning
* add docs for placeholder and fix docs control for it and other string type props
* remove unused tests and fix lint
* sigh lint
* review comments
* update new combobox example
* Add more placeholders in docs
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Co-authored-by: Devon Govett <devongovett@gmail.com>
