Move wast tests to wasmi_wast crate

[Robbepop]

This breaks a cyclic dev-dependency between wasmi and wasmi_wast which caused troubles for cargo publish.

Now all Wast based tests reside in wasmi_wast. All Wasmi integration tests remain in Wasmi and have an improved structure.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.38%. Comparing base (fc0d538) to head (7304aeb).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1403      +/-   ##
==========================================
- Coverage   69.39%   69.38%   -0.01%     
==========================================
  Files         158      158              
  Lines       14695    14698       +3     
==========================================
+ Hits        10197    10198       +1     
- Misses       4498     4500       +2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.