Incorporating a few experimental record_tests fixes

• Scrubs environments from anonymous function calls
• Adds a fallback hash of the test call stack using digest, avoiding costly look-ups using identical for comparison.

Implements a resolution for excessive duplicate test records, resulting in unnecessarily high memory needs for packages whose testing suite evaluates code in large loops.

Not an official covr release!

A quick dev release to patch an issue with duplicate test logging.

Not an official covr release!

• rebases on upstream r-lib/cov@main