use port to probe db in playground

[KanShiori]

What problem does this PR solve?

Close #2221

What is changed and how it works?

Use port not root user to probe db in playground.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

1. Create a tidb configuration that contains init SQL to init root password.

   # init.sql
   ALTER USER 'root'@'%' IDENTIFIED BY '123';
   

   # tidb.toml
   initialize-sql-file = "/root/shiori/pingcap/tiup/bin/init.sql"

2. Execute tiup playground --db.config tidb.toml.
   

3. Connect db with password successfully.
   

• No code

Code changes

• Has exported function/method change
• Has exported variable/fields change
• Has interface methods change
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation

Release notes:

NONE

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (bdf6f26) 55.54% compared to head (2aa3450) 55.53%.

❗ Current head 2aa3450 differs from pull request most recent head a43b536. Consider uploading reports for the commit a43b536 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2296      +/-   ##
==========================================
- Coverage   55.54%   55.53%   -0.01%     
==========================================
  Files         326      326              
  Lines       34421    34413       -8     
==========================================
- Hits        19117    19109       -8     
  Misses      13022    13022              
  Partials     2282     2282              

Flag	Coverage Δ
playground	15.47% <100.00%> (-0.05%)	⬇️
tiup	15.68% <ø> (ø)
unittest	22.47% <0.00%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
components/playground/main.go	59.37% <100.00%> (-0.06%)	⬇️

... and 1 file with indirect coverage changes

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[kaaaaaaang]

/lgtm

[kaaaaaaang]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: kaaaaaaang

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Needs approval from an approver in each of these files:

• OWNERS [kaaaaaaang]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-10-31 06:15:35.33369352 +0000 UTC m=+2933732.920803668: ☑️ agreed by kaaaaaaang.
• 2023-10-31 06:17:26.298401217 +0000 UTC m=+2933843.885511344: ✖️🔁 reset by KanShiori.

[ti-chi-bot]

New changes are detected. LGTM label has been removed.