Formal verification: Optimistic `DELEGATECALL`, update nonce monotonicity rule

[mmv08]

This PR:

• Adds an optimistic assumption about the DELEGATECALL operation in the Executor contract
• Update the nonce monotonicity rule to only allow it for the execTransaction method

[github-actions[bot]]

Pull Request Test Coverage Report for Build 5090552791

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+1.5%) to 98.536%

---

Totals
Change from base Build 4991446336:	1.5%
Covered Lines:	315
Relevant Lines:	316

---

💛 - Coveralls