Update cast-on-tenderly script

[SidestreamColdMelon]

Closes #389

This PR updates cast-on-tenderly script to:

• Update cast-on-tenderly outdated dependencies
• Update logic of the script to better calculate nextCastDate (and account for "office hours")
• Work with Tenderly Testnets instead of Forks

[SidestreamColdMelon]

The updated script is ready for review and can be tested with the last spell address via make cast-on-tenderly spell=0x0E9AB92e3Fad77eE35a5f702Ac56c48bAAB7B0eE. Note: please make sure to afterwards delete newly created testnet (via their UI, in the testnet settings)

[amusingaxl]

A couple of nits regarding naming for discussion, but I'm not feeling that strong about it. Feel free to keep it as it is.
At this point, it becomes a bit subjective unless we have some fairly comprehensive style guide in place, which we don't.

[SidestreamStrongStrawberry]

lgtm :)