[PR] Defer abandoned connection trace formatting [tomcat]

sainadh777 opened a new pull request, #1048:
URL: https://github.com/apache/tomcat/pull/1048

   ## Summary
   
   Complete maintained `TODO.md` item 39.1 by retaining abandoned-connection stack frames and formatting them only when the trace is actually read.
   
   ## Rationale and impact
   
   When `logAbandoned` is enabled, each connection borrow currently captures and immediately formats an exception stack trace into a `String`. Most of those traces are replaced by a later borrow without ever being reported.
   
   This change stores the captured `StackTraceElement[]` in `PooledConnection` and performs the existing string formatting lazily in `getStackTrace()`. The public String-based accessor methods remain compatible, and the text returned for a reported abandoned connection is unchanged. The regression test verifies both deferred formatting and the eventual trace contents.
   
   ## Validation
   
   All commands used JDK 25.
   
   - `ant -f modules/jdbc-pool/build.xml onetest -Dtest=AbandonedTraceTest -Dtomcat.xsl.loc=file:/private/tmp/tomcat-weekly.cfR2QA/webapps/docs/tomcat-docs.xsl -Dtomcat.project.loc=file:/private/tmp/tomcat-weekly.cfR2QA/modules/jdbc-pool/doc/project.xml` — passed: 1 test, 0 failures, 0 errors, 0 skipped.
   - `ant -f modules/jdbc-pool/build.xml test -Dtomcat.xsl.loc=file:/private/tmp/tomcat-weekly.cfR2QA/webapps/docs/tomcat-docs.xsl -Dtomcat.project.loc=file:/private/tmp/tomcat-weekly.cfR2QA/modules/jdbc-pool/doc/project.xml` — passed: all JDBC-pool functional, fairness, performance, and validation suites; 0 failures and 0 errors.
   - `ant validate -Dexecute.validate=true` — passed Checkstyle over 7,690 files.
   - `ant clean deploy` — passed clean source/distribution build.
   - `ant clean test` in an isolated Ubuntu 24.04 arm64 container (`eclipse-temurin:25-jdk-noble`, Ant 1.10.14, host networking) — passed the complete unfiltered suite in 31m38s: 41,264 tests, 0 failures, 0 errors, 315 skipped across 650 reports.
   - `output/build/bin/startup.sh`; `curl http://127.0.0.1:8080/`; `output/build/bin/shutdown.sh` in the same Linux container — HTTP 200 received and the generated Tomcat process stopped cleanly.
   
   For completeness, an initial unfiltered `ant test` on macOS was not used as the release gate because it hit platform-specific multicast routing failures, LibreSSL cipher mismatches, and pathological timing. The identical source snapshot subsequently passed the complete Linux run above.
   


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