CM-778 - Add multicaller contract with tests

[alejoloaiza]

The GuardedMulticaller contract will be deployable from Hub and therefor it needs to be included in the contracts repo. I've attached the following to this PR:

• Contract code
• Tests
• Threat model
• Audit report.

[openzeppelin-code]

CM-778 - Add multicaller contract with tests

Generated at commit: 77ea31992ccf29b7154818df67292e230c241640

🚨 Report Summary

	Severity Level	Results
Contracts	Critical High Medium Low Note Total	2 0 0 11 27 40
Dependencies	Critical High Medium Low Note Total	0 0 0 0 0 0

---

For more details view the full report in OpenZeppelin Code Inspector

[drinkcoffee]

Could you fix the slither and solhint errors that are related to this PR.

[drinkcoffee]

Add a README.md file in contracts/multicall to describe the contents of the directory. For example, see: https://github.com/immutable/contracts/tree/main/contracts/token/erc1155

In the README, the threat model and the external audit should be referenced. I expect that the version of code that was analysed for the threat model is not available in the contracts repo. As such, I would just put --- . For the external audit, you will need the git hash of the code that matches what was audited. I expect that is the code that was moved across, prior to the fixes for solhint and slither.

[rytimx]

LGTM, thanks.