[macOS,iOS] CocoaPods recommended version: 1.13.0 (flutter#135447)

Due to changes in Xcode 15, several variables such as `DT_TOOLCHAIN_DIR`
have been eliminateed in favour of others such as `TOOLCHAIN_DIR`. This
broke CocoaPods support under Xcode 15, as reported in:
CocoaPods/CocoaPods#12012

@vashworth worked around this in Flutter in:
flutter#132803

The CocoaPods issue was resolved by the following PR to their repo:
CocoaPods/CocoaPods#12009
and was released in CocoaPods 1.13.0.

Also switches from an if-else chain to a switch for CocoaPodsStatus
handling.

Related: flutter#133584
Related: flutter#132755

## Pre-launch Checklist

- [X] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [X] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [X] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [X] I signed the [CLA].
- [X] I listed at least one issue that this PR fixes in the description
above.
- [X] I updated/added relevant documentation (doc comments with `///`).
- [X] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [X] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#overview
[Tree Hygiene]: https://github.com/flutter/flutter/wiki/Tree-hygiene
[test-exempt]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo
[Features we expect every widget to implement]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#features-we-expect-every-widget-to-implement
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#handling-breaking-changes
[Discord]: https://github.com/flutter/flutter/wiki/Chat

Co-authored-by: Greg Spencer <gspencergoog@users.noreply.github.com>

packages/flutter_tools/lib/src/macos/cocoapods.dart

@@ -75,7 +75,7 @@ enum CocoaPodsStatus {
 }
 
 const Version cocoaPodsMinimumVersion = Version.withText(1, 10, 0, '1.10.0');
-const Version cocoaPodsRecommendedVersion = Version.withText(1, 11, 0, '1.11.0');
+const Version cocoaPodsRecommendedVersion = Version.withText(1, 13, 0, '1.13.0');
 
 /// Cocoapods is a dependency management solution for iOS and macOS applications.
 ///

packages/flutter_tools/test/general.shard/macos/cocoapods_test.dart

@@ -168,19 +168,19 @@ void main() {
 
     testWithoutContext('detects below recommended version', () async {
       pretendPodIsInstalled();
-      pretendPodVersionIs('1.10.5');
+      pretendPodVersionIs('1.12.5');
       expect(await cocoaPodsUnderTest.evaluateCocoaPodsInstallation, CocoaPodsStatus.belowRecommendedVersion);
     });
 
     testWithoutContext('detects at recommended version', () async {
       pretendPodIsInstalled();
-      pretendPodVersionIs('1.11.0');
+      pretendPodVersionIs('1.13.0');
       expect(await cocoaPodsUnderTest.evaluateCocoaPodsInstallation, CocoaPodsStatus.recommended);
     });
 
     testWithoutContext('detects above recommended version', () async {
       pretendPodIsInstalled();
-      pretendPodVersionIs('1.11.1');
+      pretendPodVersionIs('1.13.1');
       expect(await cocoaPodsUnderTest.evaluateCocoaPodsInstallation, CocoaPodsStatus.recommended);
     });
   });

packages/flutter_tools/test/general.shard/macos/cocoapods_validator_test.dart

@@ -40,7 +40,7 @@ void main() {
       final ValidationMessage message = result.messages.first;
       expect(message.type, ValidationMessageType.hint);
       expect(message.message, contains('CocoaPods $currentVersion out of date'));
-      expect(message.message, contains('(1.11.0 is recommended)'));
+      expect(message.message, contains('(1.13.0 is recommended)'));
       expect(message.message, contains('getting-started.html#updating-cocoapods'));
     });
   });