meta/sql: retry txn for mariadb when conflict

[jiefenghuang]

close #5442

Transaction should have an X lock and wait for it, but MariaDB’s behavior is somewhat inconsistent and it reported an error.

Case: removeDir may conflict on child node (dirStat)

[zhoucheng361]

The same problem: https://github.com/juicedata/juicefs/actions/runs/12497648861/job/34870503833

[jiefenghuang]

The same problem: https://github.com/juicedata/juicefs/actions/runs/12497648861/job/34870503833

passed.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 21.46%. Comparing base (c743889) to head (bdeb1a3).
Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/meta/sql.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5440      +/-   ##
==========================================
- Coverage   21.46%   21.46%   -0.01%     
==========================================
  Files          29       29              
  Lines       18977    18978       +1     
==========================================
  Hits         4073     4073              
- Misses      14421    14422       +1     
  Partials      483      483              

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