feat: implement mempool document counter in strategy tests

[pauldelucia]

Issue being fixed or feature implemented

Identities would broadcast documents into the mempool successfully but the transitions would potentially fail while in the mempool if the identity put more than 24 documents for a contract in, due to nonce errors.

What was done?

Pass a BTreeMap of (IdentityID, ContractID) to u64 which acts as a counter for how many documents an identity has put into the mempool for a contract. If the number is 24 or greater, we don't use that identity.

How Has This Been Tested?

Breaking Changes

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

[shumkov]

👍