Add pause mechanism

[rrousselGit]

Related Issues

fixes #1344
fixes #1207

Checklist

Before you create this PR confirm that it meets all requirements listed below by checking the relevant checkboxes ([x]).

• I have updated the CHANGELOG.md of the relevant packages.
  Changelog files must be edited under the form:

  ## Unreleased fix/major/minor
  
  - Description of your change. (thanks to @yourGithubId)

• If this contains new features or behavior changes,
  I have updated the documentation to match those changes.

[changeset-bot]

⚠️ No Changeset found

Latest commit: ed0a372

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.15%. Comparing base (36f3e20) to head (ed0a372).

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #3428      +/-   ##
==========================================
+ Coverage   94.35%   99.15%   +4.80%     
==========================================
  Files          43        5      -38     
  Lines        2339      238    -2101     
==========================================
- Hits         2207      236    -1971     
+ Misses        132        2     -130     

Files	Coverage Δ
...ckages/flutter_riverpod/lib/src/core/consumer.dart	98.87% <100.00%> (+0.05%)	⬆️

... and 38 files with indirect coverage changes