feat: new vote extenison type THRESHOLD_RAW

[lklimek]

Issue being fixed or feature implemented

Threshold-recovered vote extensions are converted into a canonical form, containing things like round and height.
Unfortunately, for Dash Platform withdrawal transactions, threshold extension signatures must be constructed using exact content of the exension, not canonical form.

What was done?

1. Added new type of vote extension, THRESHOLD_RAW, that is signed without any canonization. It also allows providing sign_request_id to be used.
2. Refactored vote extensions to a cleaner, more object-oriented architecture.
3. Refactored SignItem to use the same field names as in Dash Core QuorumSign endpoint.
4. Updated documentation.

How Has This Been Tested?

Github Actions

Breaking Changes

None

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have made corresponding changes to the documentation

For repository code-owners and collaborators only

• I have assigned this pull request to a milestone

[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[shumkov]

utACK

[shumkov]

👍