feat: bump Firebase Android SDK version to 29.0.0

[russellwheatley]

Description

Will have to merge this first: #7300

Update minSdk to 19 in build gradle on four different example apps. Android has breaking changes which mean a number of packages are not compatible with android 4.4.0 or anything below API level 19 (KitKat). see here.

Related Issues

Replace this paragraph with a list of issues related to this PR from the issue database. Indicate, which of these issues are resolved or fixed by this PR. Note that you'll have to prefix the issue numbers with flutter/flutter#.

Checklist

Before you create this PR confirm that it meets all requirements listed below by checking the relevant checkboxes ([x]).
This will ensure a smooth and quick review process. Updating the pubspec.yaml and changelogs is not required.

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• My PR includes unit or integration tests for all changed/updated/fixed behaviors (See Contributor Guide).
• All existing and new tests are passing.
• I updated/added relevant documentation (doc comments with ///).
• The analyzer (melos run analyze) does not report any problems on my PR.
• I read and followed the Flutter Style Guide.
• I signed the CLA.
• I am willing to follow-up on review comments in a timely manner.

Breaking Change

Does your PR require plugin users to manually update their apps to accommodate your change?

• Yes, this is a breaking change.
• No, this is not a breaking change.

[github-actions]

Visit the preview URL for this PR (updated for commit 5294539):

https://flutter-firebase-docs--pr7296-russell-android-sdk-fmdco1ew.web.app

_{(expires Thu, 11 Nov 2021 09:24:31 GMT)}

_{🔥 via Firebase Hosting GitHub Action 🌎}

[Salakar]

Small note that once the min sdk 19 changes are moved off into another PR this PR itself is no longer a breaking change

[aliasgarlabs]

I think this should have been a 2.0.0 release instead of 1.9.0 on pub.dev This is breaking the builds for anyone on 1.x.x and having minSdk as 16.

I suggest we roll back the update by publishing 1.10.1 on pub.dev and then publish 2.0.0 with this change.

Bonus: We can then also maintain the API 16 version with critical bug fixes.

[Salakar]

@aliasgarlabs It was done as a breaking change version in da458e2 and released as breaking for the affected packages; https://github.com/FirebaseExtended/flutterfire/blob/master/CHANGELOG.md#2021-11-04

Is something missing?