cluster/tiflash: Remove deprecated config items

[JaySon-Huang]

What problem does this PR solve?

What is changed and how it works?

• default_profile/display_name/tmp_path is no longer need since v5.4.0 (modify tiflash default config tiflash#3414)
• flash.flash_cluster is no longer need since v6.0.0 (ddl: Move TiFlash cluster manager module into TiDB tidb#29924)

Check List

Tests

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

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (3b246a3) 55.43% compared to head (12e12af) 55.39%.

❗ Current head 12e12af differs from pull request most recent head fbe2708. Consider uploading reports for the commit fbe2708 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2357      +/-   ##
==========================================
- Coverage   55.43%   55.39%   -0.05%     
==========================================
  Files         329      329              
  Lines       34841    34848       +7     
==========================================
- Hits        19314    19302      -12     
- Misses      13216    13235      +19     
  Partials     2311     2311              

Flag	Coverage Δ
cluster	44.71% <96.55%> (-0.04%)	⬇️
dm	25.44% <0.00%> (-0.01%)	⬇️
playground	15.37% <0.00%> (+<0.01%)	⬆️
tiup	33.59% <ø> (-0.05%)	⬇️
unittest	22.36% <100.00%> (+0.01%)	⬆️

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