Code cleanup and modernization:

[kamilkrzywanski]

• Removed unreachable and redundant if statements
• Fixed potential memory leak by replacing ThreadLocal.set(null) with remove()
• Replaced instanceof checks with Class.isInstance()
• Modernized list creation using List.of(...) instead of Collections.unmodifiableList(Arrays.asList(...))

[codecov]

Codecov Report

❌ Patch coverage is 0% with 44 lines in your changes missing coverage. Please review.
✅ Project coverage is 0.00%. Comparing base (a2e40f1) to head (a777b33).
⚠️ Report is 4 commits behind head on master.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...rc/main/java/com/querydsl/r2dbc/SQLSerializer.java	0.00%	17 Missing ⚠️
...src/main/java/com/querydsl/jpa/JPAExpressions.java	0.00%	3 Missing ⚠️
...l/jpa/hibernate/sql/AbstractHibernateSQLQuery.java	0.00%	3 Missing ⚠️
...java/com/querydsl/jpa/sql/AbstractJPASQLQuery.java	0.00%	3 Missing ⚠️
...a/com/querydsl/collections/CollQueryFunctions.java	0.00%	2 Missing ⚠️
...ain/java/com/querydsl/jpa/NativeSQLSerializer.java	0.00%	2 Missing ⚠️
...ain/java/com/querydsl/sql/RelationalPathUtils.java	0.00%	2 Missing ⚠️
.../com/querydsl/collections/CollQuerySerializer.java	0.00%	1 Missing ⚠️
...n/java/com/querydsl/core/DefaultQueryMetadata.java	0.00%	1 Missing ⚠️
...ain/java/com/querydsl/core/alias/AliasFactory.java	0.00%	1 Missing ⚠️
... and 9 more

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #1427    +/-   ##
=======================================
  Coverage    0.00%   0.00%            
=======================================
  Files         813     838    +25     
  Lines       31271   31579   +308     
  Branches     3550    3550            
=======================================
- Misses      31271   31579   +308     

Flag	Coverage Δ
cubrid	0.00% <0.00%> (?)
db2	0.00% <0.00%> (?)
embedded	0.00% <0.00%> (?)
examples	0.00% <0.00%> (?)
firebird	0.00% <0.00%> (?)
mongodb	0.00% <0.00%> (?)
mysql	0.00% <0.00%> (?)
oracle	0.00% <0.00%> (?)
postgresql	0.00% <0.00%> (?)
test	0.00% <0.00%> (ø)

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