Increase plugin minimum target iOS version from 9.0 to 11.0 flutter.dev/go/rfc-32-bit-ios-unsupported.

To paraphrase Stuart from #84198, the last time this was done:

Once Flutter stable no longer supports [iOS 9], we should update all the 1P plugins to match. This will eliminate the issue of deprecation warnings from the plugins in the now-common case where people build with projects that use [iOS 11] as the minimum.

Currently all of our plugins support [iOS 9] so this will affect every plugin that supports iOS, although we'll only need to update the deprecated plugins if at some point we have CI issues with the [iOS 9] support.

When we do this, we should make sure the READMEs prominently list the minimum iOS version (see also #34999)

Example: flutter/plugins#4327

Blocked by #101961

Also run app migrator #101960 by building all example projects.