kernel: De-globalize script execution cache hasher

Summary:
Move it to the ChainstateManager class.

This is a partial backport of core#30141
https://github.com/bitcoin/bitcoin/pull/30141/commits/021d38822c0e6a1b9497bcb20401c5c37e1bb84d
Depends on D18856

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D18858