ctl: replace gc_safepoint call with HTTP SDK

[JackL9u]

What problem does this PR solve?

Issue Number: ref #7300

What is changed and how does it work?

replace the doRequest(...) call with PD HTTP SDK

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[ti-chi-bot]

Hi @JackL9u. Thanks for your PR.

I'm waiting for a tikv member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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The list of commits missing DCO signoff:

• 3d48ee0 Merge branch 'dev' of https://github.com/JackL9u/pd into dev

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