explicitly handle SIGINT and SIGTERM

[joelanford]

Description of the change:

This PR adds explicit handling for SIGINT and SIGTERM, so that we can catch those signals and propagate them via a Go context to long running processes in order to perform a graceful shutdown.

Motivation for the change:

Temporary files are being left behind because defer statements are not executed when these signals are not caught and handled by the program. This PR ensures that we run defer statements prior to exiting.

Reviewer Checklist

• [ ] Implementation matches the proposed design, or proposal is updated to match implementation
• [ ] Sufficient unit test coverage
• [ ] Sufficient end-to-end test coverage
• [ ] Docs updated or added to /docs
• [ ] Commit messages sensible and descriptive

[openshift-ci[bot]]

Skipping CI for Draft Pull Request. If you want CI signal for your change, please convert it to an actual PR. You can still manually trigger a test run with /test all

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 48.53%. Comparing base (1f9e725) to head (6a917e9). Report is 15 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1448 +/- ## ========================================== + Coverage 48.47% 48.53% +0.05% ========================================== Files 136 135 -1 Lines 12814 12800 -14 ========================================== Hits 6212 6212 + Misses 5561 5547 -14 Partials 1041 1041 ```

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[openshift-ci[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: joelanford, perdasilva

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/operator-framework/operator-registry/blob/master/OWNERS)~~ [joelanford,perdasilva] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[grokspawn]

/lgtm