Restore short-prefix behind cargo flag

[jfldde]

Description

• Restore short-prefix behind cargo short-prefix flag

Main rationale for the removal in #1537 was that compile time env was not properly propagated to risczero docker build. This restores it by propagating via cargo short-prefix flag, albeit in a convoluted way.

• Automatically derive it when in running make test and make coverage
• Remove the need to keep CI_TEST_MODE in line between build and test profiles.

Note that if for whatever reason, one is running via cargo test (not advised, make test is the recommended way) directly, additional --features short-prefix is needed in order not to have a mismatch in prefix length

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.1%. Comparing base (5d1eee6) to head (67d16f1).
Report is 1 commits behind head on nightly.

Additional details and impacted files

see 3 files with indirect coverage changes