pdms: optimize upgrade pdms to avoid unnecessary primary transfer

[HuSharp]

What problem does this PR solve?

What is changed and how it works?

ref https://github.com/tikv/pd/issues/7995

When we have 3 pdms, pdms-0/pdms-1/pdms-2, when pdms-2 is primary

• upgrade pdms-2 firstly maybe transfer primary to pdms-0
• and then uprade pdms-0 will transfer primary again

upgrade pdms primary in last place can avoid  unnecessary primary transfer

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Release notes:

NONE

[HuSharp]

@xhebox PTAL, thx~

[xhebox]

/approve

[ti-chi-bot[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: xhebox

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[xhebox]

r

@xhebox PTAL, thx~

plz merge master

[ti-chi-bot[bot]]

[LGTM Timeline notifier]

Timeline:

• 2024-09-03 10:37:19.023452678 +0000 UTC m=+354363.541505603: :ballot_box_with_check: agreed by xhebox.
• 2024-09-04 02:04:13.941714236 +0000 UTC m=+409978.459767162: :heavy_multiplication_x::repeat: reset by HuSharp.
• 2024-09-04 02:10:27.686830395 +0000 UTC m=+410352.204883320: :ballot_box_with_check: agreed by xhebox.