test(e2e): enable next-gen tiflash avail test

[liubog2008]

• enable nextgen tiflash avail test and change max_execution_time to 4000ms

[ti-chi-bot]

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 43.10%. Comparing base (7620fa5) to head (cf42be2).
⚠️ Report is 3 commits behind head on feature/v2.

Additional details and impacted files

@@              Coverage Diff               @@
##           feature/v2    #6493      +/-   ##
==============================================
- Coverage       43.12%   43.10%   -0.02%     
==============================================
  Files             345      345              
  Lines           23855    23902      +47     
==============================================
+ Hits            10287    10304      +17     
- Misses          13568    13598      +30     

Flag	Coverage Δ
unittest	43.10% <ø> (-0.02%)	⬇️

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[liubog2008]

/test pull-e2e

[liubog2008]

/test pull-e2e

[liubog2008]

/test pull-e2e

[liubog2008]

/test pull-e2e

[liubog2008]

/test pull-e2e

[ti-chi-bot]

@liubog2008: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-e2e	cf42be2	link	true	/test pull-e2e

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