playground: Add --mode=tiflash-disagg

[breezewish]

What problem does this PR solve?

What is changed and how it works?

Previously #2194 introduced --mode=tidb-disagg, and later I removed it and substituted it with --mode=tidb-cse in #2386.

However, it turns out that actually we need both mode in daily development, so this PR add back tidb-disagg mode (and renamed it to tiflash-disagg mode for better name).

Check List

Tests

• Manual test (add detailed scripts or steps below)

Release notes:

playground: Add --mode=tiflash-disagg

[ti-chi-bot]

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[codecov-commenter]

Codecov Report

Attention: Patch coverage is 43.66197% with 40 lines in your changes missing coverage. Please review.

Project coverage is 42.42%. Comparing base (f57aa1d) to head (1fbe561).
Report is 1 commits behind head on master.

❗ Current head 1fbe561 differs from pull request most recent head d12dd36

Please upload reports for the commit d12dd36 to get more accurate results.

Files with missing lines	Patch %	Lines
components/playground/instance/tiflash_config.go	0.00%	18 Missing ⚠️
components/playground/playground.go	27.78%	11 Missing and 2 partials ⚠️
components/playground/instance/tidb_config.go	0.00%	2 Missing and 2 partials ⚠️
components/playground/instance/tiflash.go	50.00%	1 Missing and 1 partial ⚠️
components/playground/instance/pd_config.go	66.67%	0 Missing and 1 partial ⚠️
components/playground/instance/tikv_config.go	0.00%	0 Missing and 1 partial ⚠️
components/playground/main.go	93.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2492      +/-   ##
==========================================
- Coverage   52.11%   42.42%   -9.69%     
==========================================
  Files         335      335              
  Lines       36379    36399      +20     
==========================================
- Hits        18957    15439    -3518     
- Misses      15109    19031    +3922     
+ Partials     2313     1929     -384     

Flag	Coverage Δ
playground	16.16% <43.66%> (+0.01%)	⬆️

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-01-20 08:43:50.789585941 +0000 UTC m=+83958.120505344: ☑️ agreed by xhebox.