fix(sdk): state transition broadcast missing contract provider

[lklimek]

Issue being fixed or feature implemented

Instead of providing contract provider function, some state transition broadcast logic always returned None (meaning the contract was not found).

What was done?

• Added trait ContractProvider automatically implemented for all ContextProvider objects that makes it easy to retrieve the contract lookup fn, as required by Drive
• Added method sdk::context_provider()
• fixed existing logic

How Has This Been Tested?

In TUI, sending masternode votes

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 added "!" to the title and described breaking changes in the corresponding section if my code contains any
• I have made corresponding changes to the documentation if needed

For repository code-owners and collaborators only

• I have assigned this pull request to a milestone