tools/simulator: support simulator with multiple pds

[HuSharp]

What problem does this PR solve?

Issue Number: Ref #8135

What is changed and how does it work?

• support multiple pds , can run command like that
  tiup playground v8.0.0 --kv.binpath ./pd-simulator --kv=1 --db=0 --kv.config=../conf/simconfig.toml --pd 3
• support retry client to check leader url
• remove redundant client init and put in NewRetryClient

Test Result

tiup playground v8.0.0 --kv.binpath ./pd-simulator --kv=1 --db=0 --kv.config=../conf/simconfig.toml --pd 3

cluster metrics

add node to trigger balance

after curl --location --request POST 'http://127.0.0.1:20180/event?event=add-node'

test leader change

run ./pd-ctl member firstly to check leader

	...
  "leader": {
    "name": "pd-0",
    "member_id": 3474484975246189105,
    "peer_urls": [
      "http://127.0.0.1:2380"
    ],
    "client_urls": [
      "http://127.0.0.1:2379"
    ],
	...

transfer leader

$ ./pd-ctl member leader transfer pd-1
Success!

heartbeat upload

remove node to trigger balance

curl --location --request POST 'http://127.0.0.1:20180/event?event=down-node'

Check List

Tests

• Manual test (add detailed scripts or steps below)

Release note

None.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.27%. Comparing base (fbd6bd2) to head (d140be6).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8304      +/-   ##
==========================================
- Coverage   77.38%   77.27%   -0.11%     
==========================================
  Files         470      470              
  Lines       61356    61356              
==========================================
- Hits        47480    47413      -67     
- Misses      10310    10381      +71     
+ Partials     3566     3562       -4     

Flag	Coverage Δ
unittests	77.27% <ø> (-0.11%)	⬇️

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: nolouch, rleungx

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-06-18 09:17:16.887705035 +0000 UTC m=+106363.373193860: ☑️ agreed by rleungx.
• 2024-06-19 06:31:34.742986805 +0000 UTC m=+182821.228475635: ☑️ agreed by nolouch.

[nolouch]

/merge

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