Fix typos in rollup.go, executor.go, staking_upgrade.ts, and L2Staking.t.sol

[Dimitrolito]

1. L2Staking.t.sol:

   • Corrected "sequncer" to "sequencer" in comments describing test scenarios.

2. staking_upgrade.ts:

   • Fixed "implemention" to "implementation" in a log message.

3. executor.go:

   • Corrected "alllowed" to "allowed" in error messages.

4. rollup.go:

   • Fixed "gernerate" to "generate" in an error message.

[chengwenxi]

Good catch! Thank you.