Update all plugins minimum from macOS 10.11 to 10.13

[jmagman]

Increase plugin minimum target iOS version from macOS 10.11 to 10.13. #107739

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

Once Flutter stable no longer supports [macOS 10.13], 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 [macOS 10.13] as the minimum.

Currently all of our plugins support [macOS 10.11] 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 [macOS 10.13] support.

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

Example: flutter/plugins#4327

https://github.com/flutter/plugins/blob/5712aedbc5d1ad588056fd8ad7d947d5e39be85c/packages/url_launcher/url_launcher_macos/macos/url_launcher_macos.podspec#L18

Also run app migrator #107689 by building all example projects.