#2123: configure Checkstyle suppression for legitimate System.out usages

[maybeec]

This PR fixes #2123

Internal enhancement (developers only) — preparation for the linting harness, scoped to the
System.out / System.err Checkstyle rule. Labelled internal, so no CHANGELOG entry.

Implemented changes:

• checkstyle.xml: gave the System.out/System.err rule the id SystemOut and added two
  suppression mechanisms so legitimate usages no longer block the build:
  • SuppressWithNearbyCommentFilter — inline, single-line: a trailing // checkstyle:ignore SystemOut - reason on the offending line (limited to that line only).
  • SuppressionSingleFilter — whole-file, scoped to the log package (the logging implementation
    legitimately writes to System.out/System.err); only the SystemOut rule is suppressed there.
• Marked the legitimate usages with inline markers: AbstractIdeContext (log just failed, point to
  logfile), GraalVmHelper (native-image bootstrap before logging), CompleteCommandlet (bash
  completion must reach stdout), Ideasy (option parsing before logger init), OperatingSystem
  (static OS detection, no context).
• Cleaned up the accidental usages: UrlSecurityFile now logs via the SLF4J/jline logger; removed
  leftover debug prints from PycharmTest, IntellijTest, FileAccessImplTest.
• EclipseWorkspaceLockChecker (+ its test): adopted the exact java.io.File → java.nio.file.Path
  and System.out → SLF4J-logger change from #2118: replace java.io.File usages with java.nio.file.Path #2120 so both branches merge without conflict.

Out of scope and intentionally left as-is: the printStackTrace violation in
IdeLogExceptionDetails (a different rule), and three further System.out sites already handled by
#2120 / to be addressed with their respective rules.

Testing instructions

1. In cli/, run mvn checkstyle:check — the System.out/System.err sites listed above no longer
   produce violations (the remaining printStackTrace in IdeLogExceptionDetails is a different
   rule and out of scope).
2. In cli/, run mvn -Dtest=PycharmTest,IntellijTest,FileAccessImplTest,EclipseWorkspaceLockCheckerTest test
   — all pass.
3. Run mvn clean test — build is green.

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Checklist for this PR

• When running mvn clean test locally all tests pass and build is successful
• PR title is of the form #«issue-id»: «brief summary» (e.g. #921: fixed setup.bat). If no issue ID exists, title only.
• PR top-level comment summarizes what has been done and contains link to addressed issue(s)
• PR and issue(s) have suitable labels
• Issue is set to In Progress and assigned to you or there is no issue (might happen for very small PRs)
• You followed all coding conventions
• You have added the issue implemented by your PR in CHANGELOG.adoc unless issue is labeled with internal — labelled internal, no CHANGELOG entry needed
• You have formulated clear instructions on how to test your contribution under "Testing instructions"

[coveralls]

Coverage Report for CI Build 29487708149

Warning

Build has drifted: This PR's base is out of sync with its target branch, so coverage data may include unrelated changes.
Quick fix: rebase this PR. Learn more →

Coverage increased (+0.02%) to 72.229%

Details

• Coverage increased (+0.02%) from the base build.
• Patch coverage: No coverable lines changed in this PR.
• 74 coverage regressions across 4 files.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

74 previously-covered lines in 4 files lost coverage.

File	Lines Losing Coverage	Coverage
com/devonfw/tools/ide/context/AbstractIdeContext.java	43	68.99%
com/devonfw/tools/ide/url/model/file/UrlSecurityFile.java	19	11.11%
com/devonfw/tools/ide/locking/EclipseWorkspaceLockChecker.java	8	39.29%
com/devonfw/tools/ide/cli/GraalVmHelper.java	4	0.0%

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Coverage Stats

Relevant Lines:	16734
Covered Lines:	12592
Line Coverage:	75.25%
Relevant Branches:	7464
Covered Branches:	4886
Branch Coverage:	65.46%
Branches in Coverage %:	Yes
Coverage Strength:	3.18 hits per line

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💛 - Coveralls

[hohwille]

@maybeec thanks for pushing this forward. 👍

[hohwille]

QA retest:
This is just an internal refactoring so no explicit feature to test in end-to-end test. I tested some basic stuff with the latest nightly SNAPSHOT release on Windows and verified that System.out is only used in few places that have commented with checkstyle:ignore.
I found that we also have a groovy script full of System.out statements without annotations but I verified that our commit hook is only checking *.java and *.groovy currently does not have linting.
Therefore, I set QA approved label.