[cmake] Create a lib specifically for script related components

Summary: This somewhat detangle the mess that the codebase is in. Most notably, sign.cpp uses part that are defined in interpreter.cpp, but there was no dependency, and it an break.

Test Plan:

ninja check

Run ARM, AArch64, win32 and win64 builds.

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D4205