enhancement: set TerminationGracePeriodSeconds with value in be.conf

[xiacongling]

TerminationGracePeriodSeconds are set by operator for dcr BEs, but not for ddc compute group BEs.

This PR set compute group BE Pod template's TerminationGracePeriodSeconds with config value grace_shutdown_wait_seconds in be.conf

What problem does this PR solve?

Issue Number: close #475

Related PR: N/A

Problem Summary:

Release note

graceful shutdown for disaggregated doris backends

Check List (For Author)

• Test

  • Regression test
  • Unit Test
  • Manual test (add detailed scripts or steps below)
  • No need to test or manual test. Explain why:
    • This is a refactor/code format and no logic has been changed.
    • Previous test can cover this change.
    • No code files have been changed.
    • Other reason

• Behavior changed:

  • No.
  • Yes.

• Does this need documentation?

  • No.
  • Yes.

Check List (For Reviewer who merge this PR)

• Confirm the release note
• Confirm test cases
• Confirm document
• Add branch pick label

[xiacongling]

@catpineapple @intelligentfu8 can you review this pr?