[google_maps_flutter] Add heatmap support

[Rexios80]

Transferred from flutter/plugins#5274

Adds heatmap support for web, iOS, and Android

List which issues are fixed by this PR. You must list at least one issue.

Fixes #33586
Fixes #86811

If you had to change anything in the flutter/tests repo, include a link to the migration guide as per the breaking change policy.

IF YOU WANT TO USE THIS NOW

pubspec.yaml:

dependencies:
  google_maps_flutter: ^2.6.0

dependency_overrides:
  google_maps_flutter:
    git:
      url: https://github.com/Rexios80/packages_flutter
      ref: 01ab1db2d2ac3a13d70d25576c8aab0c5ba38a7c
      path: packages/google_maps_flutter/google_maps_flutter
  google_maps_flutter_web:
    git:
      url: https://github.com/Rexios80/packages_flutter
      ref: 01ab1db2d2ac3a13d70d25576c8aab0c5ba38a7c
      path: packages/google_maps_flutter/google_maps_flutter_web
  google_maps_flutter_android:
    git:
      url: https://github.com/Rexios80/packages_flutter
      ref: 01ab1db2d2ac3a13d70d25576c8aab0c5ba38a7c
      path: packages/google_maps_flutter/google_maps_flutter_android
  google_maps_flutter_ios:
    git:
      url: https://github.com/Rexios80/packages_flutter
      ref: 01ab1db2d2ac3a13d70d25576c8aab0c5ba38a7c
      path: packages/google_maps_flutter/google_maps_flutter_ios
  google_maps_flutter_platform_interface:
    git:
      url: https://github.com/Rexios80/packages_flutter
      ref: 01ab1db2d2ac3a13d70d25576c8aab0c5ba38a7c
      path: packages/google_maps_flutter/google_maps_flutter_platform_interface

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter. (Unlike the flutter/flutter repo, the flutter/plugins repo does use dart format.)
• I signed the CLA.
• The title of the PR starts with the name of the plugin surrounded by square brackets, e.g. [shared_preferences]
• I listed at least one issue that this PR fixes in the description above.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or this PR is exempt from version changes.
• I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

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

[reidbaker]

Thank you for your contribution. It looks like the tests are failing. Before we review the PR, please see what you can do to resolve the test failures. If you are unsure how to proceed, please reach out for help on the #hackers-new channel.

[Rexios80]

@reidbaker The actions seem to only be failing due to the required dependency overrides since this PR requires changes to the platform interface. Until we are ready to split out the platform interface changes into their own PR and get that merged, the actions will continue to fail on this PR.

[Rexios80]

@stuartmorgan The example ios app Podfile needs to specify platform :ios, '13.0' in order to use the latest Google Maps iOS Cocoapod. Should I make a PR just for that or include it here?

[stuartmorgan]

The example ios app Podfile needs to specify platform :ios, '13.0' in order to use the latest Google Maps iOS Cocoapod.

Why do you need the latest version? It looks like building and testing are passing as-is; doesn't that mean the APIs you are using are available back to the oldest version that supports 11.0?

[Rexios80]

I don't necessarily need it, but since we were seeing behavior changes between versions on Android I thought it might be good to make sure the example app is actually using the latest.

[stuartmorgan]

LGTM! 🚀

[Rexios80]

And it's released! Thank you all so much for the reviews over the past two years.