fix(material/input): uncessary scroll bar on auto-resize textarea in some cases (#21619)
fix(material/input): uncessary scroll bar on auto-resize textarea in some cases (#21619)

It's common for apps to set `box-sizing: border-box` on all elements in the app which ends
up causing unnecessary scroll bars on auto-resizing textareas. These changes explicitly
set `box-sizing: content-box` to fix it.

Note that ideally we'd do this at the `cdk/text-field` level since it is the one responsible
for resizing the textarea, but we generally try to avoid changing the user's layout through
the CDK.

Fixes #21560.
josephperrott/material2,DevVersion/material2,angular/components,mmalerba/material2,josephperrott/material2,josephperrott/material2,mmalerba/material2,andrewseguin/material2,DevVersion/material2,crisbeto/material2,mmalerba/material2,angular/components,angular/components,crisbeto/material2,DevVersion/material2,crisbeto/material2,andrewseguin/material2,andrewseguin/material2,josephperrott/material2,crisbeto/material2,DevVersion/material2,andrewseguin/material2,josephperrott/material2,andrewseguin/material2,DevVersion/material2,mmalerba/material2,angular/components,mmalerba/material2