telemetry(amazonq): Add metrics utility to instrument generated patch…

[ctidd]

telemetry(amazonq): Add metrics utility to instrument generated patches applied to existing code.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Description

Problem: We do not yet instrument "lines of code generated" or "lines of code accepted" for patches to existing files. To do this requires inspecting a diff and applying some heuristics around what we count, focused on collecting the count of generated or accepted code (i.e. sum of lines inserted/modified).

Solution: This utility enables us to diff the before/after content of a file and report the number of lines of code in the diff. The solutions counts inserted/modified lines, and counts characters within each line, excluding leading and trailing whitespace.

The solution may be considered naive in the following ways, by design:

• Performing a whitespace-sensitive diff
• Counting chars, as opposed to graphemes
• Counting empty lines and trailing newlines
• Not counting deleted lines

The solution is tested to pin down these behaviors, which may be subject to future changes.

Checklist

• My code follows the code style of this project
• I have added tests to cover my changes
• A short description of the change has been added to the CHANGELOG if the change is customer-facing in the IDE.
• I have added metrics for my changes (if required)

License

I confirm that my contribution is made under the terms of the Apache 2.0 license.