Linter service clears lint results too greedily #1127

Bug Description

When implementing a full lint lifecycle, both pre and post linters are run on an artifact. This requires LinterService.run() to be called twice, since each stage must be invoked individually (LinterService.run(Stage.PRE, ctx); LinterService.run(Stage.POST, ctx)).

This means:

• Lint results are broken up in a manner that appears arbitrary to users; pre/post really are implementation details.
• LinterService.summary() forgets the results of the first run, which could result in false positives for 0 return codes.

To Reproduce

Implement two custom linters, one pre- and one post-, and then try to run both of them as you might during a pack command's final steps.

part yaml

N/A

Relevant log output

N/A