Add NMEA receiving feature (null safety update)

[juanmanjarres]

✨ What kind of change does this PR introduce? (Bug fix, feature, docs update...)

New feature.

⤵️ What is the current behavior?

There is no current option to receive NMEA messages.

🆕 What is the new behavior (if this is a feature change)?

With this PR, you can receive NMEA messages (only on Android N and above, no iOS due to limitations).

💥 Does this PR introduce a breaking change?

No

🐛 Recommendations for testing

📝 Links to relevant issues/docs

Closes #605, closes #561
This PR takes most changes from #605 and updates them to null safety and the latest changes from master.

🤔 Checklist before submitting

• I made sure all projects build.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy.
• I updated CHANGELOG.md to add a description of the change.
• I followed the style guide lines (code style guide).
• I updated the relevant documentation.
• I rebased onto current master.

[codecov]

Codecov Report

Merging #819 (0fe59c1) into master (06649f4) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##            master      #819    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files            1        18    +17     
  Lines           27       277   +250     
==========================================
+ Hits            27       277   +250     

Impacted Files	Coverage Δ
...terface/lib/src/geolocator_platform_interface.dart	100.00% <100.00%> (ø)
...src/implementations/method_channel_geolocator.dart	100.00% <100.00%> (ø)
...latform_interface/lib/src/models/nmea_message.dart	100.00% <100.00%> (ø)
...rs/permission_definitions_not_found_exception.dart	100.00% <0.00%> (ø)
...or_platform_interface/lib/src/models/position.dart	100.00% <0.00%> (ø)
...e/lib/src/errors/already_subscribed_exception.dart	100.00% <0.00%> (ø)
...e/lib/src/errors/invalid_permission_exception.dart	100.00% <0.00%> (ø)
...orm_interface/lib/src/models/location_options.dart	100.00% <0.00%> (ø)
...rors/permission_request_in_progress_exception.dart	100.00% <0.00%> (ø)
... and 11 more

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[juanmanjarres]

Note: to avoid conflicts, I was using my own GitHub fork for the packages, so the analyzer checks failed. I will update their versions, but note that most checks will fail as I have to update the pubspecs for android, geolocator and geolocator_platform_interface.

[juanmanjarres]

Closed in favour of #932 as it implements NMEA with the latest changes.