[chronik] Fix handling of -chronikelectrummaxhistory

Summary: The option is assiging a 64 bits signed integer into a 32 bit unsigned integer, which might not work. This diff makes sure the value is withing bounds.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, tobias_ruck

Reviewed By: #bitcoin_abc, tobias_ruck

Subscribers: tobias_ruck

Differential Revision: https://reviews.bitcoinabc.org/D17683