client: directly save tls config

[CabinfeverB]

What problem does this PR solve?

Issue Number: ref #7576

What is changed and how does it work?

no need to transfer TLSConfig to tls.Config.
And after replacing it, we can check whether use tls more expediently.

Check List

Tests

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

Code changes

• Has the configuration change
• Has HTTP API interfaces changed (Don't forget to add the declarative for the new API)
• Has persistent data change

Side effects

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

Related changes

• PR to update pingcap/docs/pingcap/docs-cn:
• PR to update pingcap/tiup:
• Need to cherry-pick to the release branch

Release note

None.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• JmPotato
• rleungx

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[rleungx]

How about
tlsCfg, err := &tlsutil.TLSConfig{...}.ToTLSConfig()?

[codecov]

Codecov Report

Merging #7662 (691b91c) into master (754095a) will decrease coverage by 0.11%.
Report is 1 commits behind head on master.
The diff coverage is 55.55%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7662      +/-   ##
==========================================
- Coverage   73.87%   73.76%   -0.11%     
==========================================
  Files         429      429              
  Lines       47376    47379       +3     
==========================================
- Hits        35000    34951      -49     
- Misses       9392     9428      +36     
- Partials     2984     3000      +16     

Flag	Coverage Δ
unittests	73.76% <55.55%> (-0.11%)	⬇️

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[JmPotato]

/merge

[ti-chi-bot]

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[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 120728c