Generate regex for cleaning the root path in Failure only once

[fnordfish]

Description

When Failure cleans the given root path from a backtrace, the Rexexp used for that will only be generated once, instead of once per line. It also uses sub! instead of gsub! b/c we can safely break after the first match.

Types of Changes

• Performance improvement.

Testing

• [x] I added tests for my changes.
• [x] I tested my changes locally.
• [ ] I tested my changes in staging.
• [ ] I tested my changes in production.

[ioquatix]

Great, thanks for this.