[chronik] add macros to extract params from a JSONRPC request

Summary:
The get_param! and get_optional_param! macros will be reused a lot as more methods are added.

Depends on D17314
Ref T3598

Test Plan: ninja check-functional

Reviewers: #bitcoin_abc, Fabien, tobias_ruck

Reviewed By: #bitcoin_abc, Fabien, tobias_ruck

Subscribers: tobias_ruck, Fabien

Maniphest Tasks: T3598

Differential Revision: https://reviews.bitcoinabc.org/D17347