Feat: Introduce Hint data bag

[denrase]

📜 Description

Introduces a custom type for all hint properties, with a Map like interface.

Relates to #510

💡 Motivation and Context

Users can attach more than one primitive or object to API which takes a hint parameter.

This is a breaking change.

💚 How did you test it?

Added unit tests.

📝 Checklist

• I reviewed submitted code
• I added tests to verify changes
• I updated the docs if needed
• All tests passing
• No breaking changes

🔮 Next steps

I have opted not to add Attachments or Screenshot to the scope of this PR. Should we do this separately and also define what to do with this data in the SDK?

[github-actions]

	Fails
🚫	Please consider adding a changelog entry for the next release.

	Messages
📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

Instructions and example for changelog

Please add an entry to CHANGELOG.md to the "Unreleased" section. Make sure the entry includes this PR's number.

Example:

## Unreleased

- Introduce `Hint` data bag ([#1136](https://github.com/getsentry/sentry-dart/pull/1136))

If none of the above apply, you can opt out of this check by adding #skip-changelog to the PR description.

Generated by 🚫 dangerJS against bfe155c

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (v7.0.0@5460121). Click here to learn what that means.
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff            @@
##             v7.0.0    #1136   +/-   ##
=========================================
  Coverage          ?   88.07%           
=========================================
  Files             ?      121           
  Lines             ?     3815           
  Branches          ?        0           
=========================================
  Hits              ?     3360           
  Misses            ?      455           
  Partials          ?        0           

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[marandaneto]

@denrase so one thing that has to be done is, the SDK should create a Hint if none is provided, for example, Java does it on SentryClient#captureEvent.
Also, we should always pass the original object as a hint when automatically capturing events, for example.
LoggingIntegration#_onLog calls captureEvent and addBreadcrumb not passing the record as a hint, we should do that for all the integrations that call captureEvent, captureException, etc...

[marandaneto]

Btw before merging this, I believe we need to update the branch v7.0.0 with the latest main to avoid more conflicts.

[denrase]

@marandaneto Hope i found all occurences where we can pass a hint. Made an expeption (pun!) to exceptions and stacktraces, as they are already passed. Let me know what you think.

[marandaneto]

Left 2 comments but overall LGTM