Fix count and show timeseries follow-up

[Caideyipi]

Summary

• Backport Fix count and show timeseries follow-up #17804 to rc/2.0.10.
• Resolve region scan/count timeseries conflicts, including logical view active count handling and internal database visibility checks.
• Add compatibility for schema source region skipping on this branch.

Verification

• mvn spotless:apply -pl iotdb-core/datanode,integration-test -P with-integration-tests
• git diff --cached --check
• Targeted datanode tests were attempted, but datanode compilation is currently blocked by existing generated-source/Thrift cache mismatches such as missing IFill/PipeSubscribeHeartbeatReq and parser/thrift API mismatches.

[sonarqubecloud]

Quality Gate passed

Issues
17 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
3.7% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

❌ Patch coverage is 48.77384% with 188 lines in your changes missing coverage. Please review.
✅ Project coverage is 40.85%. Comparing base (8da40c6) to head (3c45f43).

Files with missing lines	Patch %	Lines
...db/db/queryengine/plan/analyze/AnalyzeVisitor.java	38.82%	52 Missing ⚠️
...iotdb/db/queryengine/common/TimeseriesContext.java	51.54%	47 Missing ⚠️
...tor/source/ActiveTimeSeriesRegionScanOperator.java	0.00%	47 Missing ⚠️
...an/relational/security/TreeAccessCheckVisitor.java	83.07%	11 Missing ⚠️
...r/plan/node/metadata/read/TimeSeriesCountNode.java	50.00%	7 Missing ⚠️
...b/queryengine/plan/planner/LogicalPlanVisitor.java	0.00%	6 Missing ⚠️
...ueryengine/plan/planner/OperatorTreeGenerator.java	0.00%	6 Missing ⚠️
...n/node/metadata/read/LevelTimeSeriesCountNode.java	53.84%	6 Missing ⚠️
...operator/schema/CountGroupByLevelScanOperator.java	57.14%	3 Missing ⚠️
...execution/operator/schema/SchemaCountOperator.java	33.33%	2 Missing ⚠️
... and 1 more

Additional details and impacted files

@@ Coverage Diff @@## rc/2.0.10 #18050 +/- ##
===============================================
+ Coverage 40.82% 40.85% +0.03% 
Complexity 2610 2610 ===============================================
Files 5185 5185 Lines 351013 351317 +304 Branches 44895 44953 +58 ===============================================
+ Hits 143286 143528 +242 - Misses 207727 207789 +62 

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