fix: enable shared sharding system accounts by default

[leon-inf]

close #9887

[apecloud-bot]

Auto Cherry-pick Instructions

Usage:
  - /nopick: Not auto cherry-pick when PR merged.
  - /pick: release-x.x [release-x.x]: Auto cherry-pick to the specified branch when PR merged.

Example:
  - /nopick
  - /pick release-1.0

[leon-inf]

/pick release-1.0

[codecov]

Codecov Report

❌ Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 50.85%. Comparing base (6e1e349) to head (44eed66).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
...ps/cluster/transformer_cluster_sharding_account.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9890      +/-   ##
==========================================
+ Coverage   50.79%   50.85%   +0.06%     
==========================================
  Files         539      539              
  Lines       58214    58215       +1     
==========================================
+ Hits        29568    29604      +36     
+ Misses      25745    25712      -33     
+ Partials     2901     2899       -2     

Flag	Coverage Δ
unittests	50.85% <0.00%> (+0.06%)	⬆️

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[apecloud-bot]

/cherry-pick release-1.0

[apecloud-bot]

🤖 says: cherry pick action finished successfully 🎉!
See: https://github.com/apecloud/kubeblocks/actions/runs/19691358703