feat: combine v1.7.0 and v1.8.0 upgrade scripts (#1628)

**Motivation:**

Hourglass and Multichain will be launching together. We need to combine
the upgrade sciprts

**Modifications:**

- Combine `v1.8.0` into `v1.7.0`. Rename `v1.7.0` to
`v1.7.0-v1.8.0-multichain-hourglass-combined`
- Add checks for `TaskMailbox`
- Remove stale upgrade scripts

**Result:**

Mainnet release ready

Author: ypatil12