Testing and coverage fixes

[jsiirola]

Fixes # .

Summary/Motivation:

This contains some minor updates to the test infrastructure

Changes proposed in this PR:

• Attempt to resolve a test that fails intermittently under PyPy
• Generalize / resync the GHA workflows in preparation for exploring use of reusable workflows
• Update the codecov-action from v4 to v5
• Rework some of the codecov.yml configuration to (hopefully) get codecov to report PR coverage more often (see also Bug Report: Pull reports do not track PR branches codecov/feedback#692)
  • Move the red/yellow threshold from 50% to 70% (codecov's default)
  • Move the yellow/green threshold from 100% to 98%
  • Allow reporting before all jobs are complete / do not wait for CI before reporting

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