feat: parallel deletion of runners

[yanksyoon]

Applicable spec: N/A

Overview

• Uses thread pool executor to concurrently submit delete requests, which includes:
  • Concurrent platform provider (GitHub) delete
  • Concurrent VM delete from OpenStack
  • Concurrent metrics fetching over SSH

Rationale

• To remove serial delete bottleneck in reconcile loop.

Juju Events Changes

Module Changes

Library Changes

Checklist

• The charm style guide was applied.
• The contributing guide was applied.
• The changes are compliant with ISD054 - Managing Charm Complexity
• The documentation for charmhub is updated.
• The PR is tagged with appropriate label (urgent, trivial, complex).
• The changelog is updated with changes that affects the users of the charm.

No user facing changes.

[yanksyoon]

PR review help comments

[github-actions]

Test results for commit b06bf0b

Test coverage for b06bf0b

Wrote XML report to coverage/coverage.xml

Static code analysis report

Run started:2025-07-24 02:23:38.822381

Test results:
  No issues identified.

Code scanned:
  Total lines of code: 2024
  Total lines skipped (#nosec): 2
  Total potential issues skipped due to specifically being disabled (e.g., #nosec BXXX): 1

Run metrics:
  Total issues (by severity):
  	Undefined: 0
  	Low: 0
  	Medium: 0
  	High: 0
  Total issues (by confidence):
  	Undefined: 0
  	Low: 0
  	Medium: 0
  	High: 0
Files skipped (0):

[github-actions]

TICS Quality Gate

❌ Failed

The following errors have occurred during analysis:

❌ [ERROR 5333] Project database 'github-runner-operator' already is connected to a started TICSQServer process that has not registered a stop time. To avoid data corruption, analysis is aborted. Details of the other TICSQServer process: started at 2025-07-09 14:32:08.000 by user ubuntu.

.github/workflows/tics.yaml / TICS / TICS GitHub Action