Fix importer tests using mirror_node user

[steven-sheehy]

Description:

• Change importer tests from running as mirror_node to mirror_importer db user
• Fix some test regressions due to use of regular JdbcOperations

Checklist

• Documented (Code comments, README, etc.)
• Tested (unit, integration, etc.)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.18%. Comparing base (883b425) to head (1d7806d).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main   #10309   +/-   ##
=========================================
  Coverage     92.18%   92.18%           
  Complexity     8005     8005           
=========================================
  Files           980      980           
  Lines         33444    33444           
  Branches       4218     4218           
=========================================
+ Hits          30830    30831    +1     
  Misses         1612     1612           
+ Partials       1002     1001    -1     

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[jnels124]

lgtm

[xin-hedera]

LGTM