[CMAKE] Make the FindRapicheck module consistent with the other modules

Summary: Based on the facilities from D5339, only minor changes.

Test Plan:

cmake -GNinja .. -DENABLE_PROPERTY_BASED_TESTS=ON
ninja check

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D5452