feat: require analyzer: ^5.12.0

[amondnet]

Describe the changes proposed in this Pull Request.

If the PR fixes a specific issue, reference the issue with Fixes #.

Fixes #928
Fixes #929
Fixes #930

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Pull Request Checklist

• If the changes are being made to code, ensure the version in pubspec.yaml is updated.
• Increment the major/minor/patch/patch-count, depending on the complexity of change
• Add the necessary unit tests to ensure the coverage does not drop
• Update the Changelog to include all changes made in this PR, organized by version
• Run the melo run set_version command from the root directory
• Include the necessary reviewers for the PR
• Update the docs if there are any API changes or additions to functionality

[codecov]

Codecov Report

Merging #934 (69a73c1) into master (6e6378c) will not change coverage.
Report is 4 commits behind head on master.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #934   +/-   ##
=======================================
  Coverage   98.99%   98.99%           
=======================================
  Files          56       56           
  Lines        1987     1987           
=======================================
  Hits         1967     1967           
  Misses         20       20           

Flag	Coverage Δ
flutter_mobx	100.00% <ø> (ø)
mobx	98.55% <ø> (ø)
mobx_codegen	100.00% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
mobx_codegen/lib/src/template/util.dart	100.00% <ø> (ø)
mobx_codegen/lib/src/type_names.dart	100.00% <100.00%> (ø)

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[HudsonAfonso]

@pavanpodila, @fzyzcjy news?

[fzyzcjy]

LGTM! (since just a simple migration of APIs)