Add /terminate API (#6745)

[nikitakalyanov]

this is to speed up suspends, see
https://github.com/neondatabase/cloud/issues/10284

Cherry-pick to release branch to build new compute images

Problem

Summary of changes

Checklist before requesting a review

• I have performed a self-review of my code.
• If it is a core feature, I have added thorough tests.
• Do we need to implement analytics? if so did you add the relevant metrics to the dashboard?
• If this PR requires public announcement, mark it with /release-notes label and add several sentences in this section.

Checklist before merging

• Do not forget to reformat commit message to not include the above checklist

Problem

Summary of changes

Checklist before requesting a review

• I have performed a self-review of my code.
• If it is a core feature, I have added thorough tests.
• Do we need to implement analytics? if so did you add the relevant metrics to the dashboard?
• If this PR requires public announcement, mark it with /release-notes label and add several sentences in this section.

Checklist before merging

• Do not forget to reformat commit message to not include the above checklist

[koivunej]

Wrote some nits before understanding this might be needed fast, so feel free to ignore them.

I cannot see any obvious problems.

[github-actions]

2442 tests run: 2325 passed, 0 failed, 117 skipped (full report)

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Flaky tests (1)

Postgres 16

• test_vm_bit_clear_on_heap_lock: debug

Code coverage (full report)

• functions: 55.8% (12930 of 23173 functions)
• lines: 82.5% (69938 of 84785 lines)

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_{The comment gets automatically updated with the latest test results
0e9985e at 2024-02-21T11:25:15.960Z :recycle:}