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 :white_check_mark:

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

:exclamation: 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

```diff @@ 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](https://app.codecov.io/gh/pingcap/tiup/pull/2296/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pingcap) | Coverage Δ | | |---|---|---| | [playground](https://app.codecov.io/gh/pingcap/tiup/pull/2296/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pingcap) | `15.47% <100.00%> (-0.05%)` | :arrow_down: | | [tiup](https://app.codecov.io/gh/pingcap/tiup/pull/2296/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pingcap) | `15.68% <ø> (ø)` | | | [unittest](https://app.codecov.io/gh/pingcap/tiup/pull/2296/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pingcap) | `22.47% <0.00%> (+0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pingcap#carryforward-flags-in-the-pull-request-comment) to find out more. | [Files](https://app.codecov.io/gh/pingcap/tiup/pull/2296?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pingcap) | Coverage Δ | | |---|---|---| | [components/playground/main.go](https://app.codecov.io/gh/pingcap/tiup/pull/2296?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pingcap#diff-Y29tcG9uZW50cy9wbGF5Z3JvdW5kL21haW4uZ28=) | `59.37% <100.00%> (-0.06%)` | :arrow_down: | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/pingcap/tiup/pull/2296/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pingcap)

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[kaaaaaaang]

/lgtm

[kaaaaaaang]

/approve

[ti-chi-bot[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: kaaaaaaang

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/pingcap/tiup/blob/master/OWNERS)~~ [kaaaaaaang] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[ti-chi-bot[bot]]

[LGTM Timeline notifier]

Timeline:

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

[ti-chi-bot[bot]]

New changes are detected. LGTM label has been removed.