feat: add option to define terminationGracePeriodSeconds

[Helinanu]

Requirements

• [x] I have added test coverage for new or changed functionality
• [x] I have followed the repository's pull request submission guidelines
• [x] I have validated my changes against all supported platform versions

Related issues Related issue, setting terminationGracePeriodSeconds is needed when combined with long sleep in preStopHooks https://github.com/launchdarkly/ld-relay-helm/issues/56

Describe the solution you've provided

Simple addition to enable defining terminationGracePeriodSeconds for ld-relay

Describe alternatives you've considered

No alternatives considered

Additional context

Add any other context about the pull request here.

[keelerm84]

Thank you for your contribution! This has been released in 3.3.0. Have a great week!