Context

The gas cost for merge_types is currently under-estimated (in Hangzhou and alpha). This MR updates that cost.

NB: this should be merged to alpha but also cherry-picked for Hangzhou2

Checklist

Document the interface of any function added or modified (see the coding guidelines)
Document any change to the user interface, including configuration parameters (see node configuration)
Provide automatic testing (see the testing guide).
For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, the Development Version section of CHANGES.md for everything else).
Select suitable reviewers using the Reviewers field below.
Select as Assignee the next person who should take action on that MR