[Textarea] New Textarea component

[mj12albert]

Part of https://github.com/mui/base-ui/issues/71

This PR adds a Textarea component that contains logic ported from @mui/base/Input, and thinly wraps TextareaAutosize

TextareaAutosize has been removed from the docs and replaced with Textarea (under "Inputs" instead of "Utils"), though the content is largely the same

TODO

• [ ] Shared utils - resolveClassName, CommonProps, getStyleHookProps
• [ ] Finalize new API - https://www.notion.so/mui-org/base-ui-Textarea-API-8c265901b51345ce905eef0e6de03511?pvs=4

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• [x] I have followed (at least) the PR section of the contributing guide.

[michaldudak]

Putting this on hold until we're closer to the release and can assess the need for this component (specifically, if CSS field sizing is widely supported).