#1405: Fix integration test order dependency

[maybeec]

This PR fixes #1405

This PR addresses the issue where integration tests were failing when executed in alphabetical order due to environment interference between tests.

Root Cause

The original issue occurred when verify-longpaths.sh was renamed to ensure-longpaths.sh, causing it to run first alphabetically. The test used $IDE -f install which performs a forced full IDEasy installation that modifies the global environment and interferes with subsequent tests. The install-intellij.sh test expected a clean environment for tool-specific installation.

Implemented changes:

• Improved OS detection: Added doGetOsType() function to detect OS type based on $OSTYPE instead of relying on GitHub workflow matrix variables (MATRIX_OS). This makes tests more portable and runnable outside GitHub Actions.
• Updated test infrastructure: Modified doDownloadSnapshot(), doIsMacOs(), and doIsWindows() functions to use the new OS detection method.
• Test isolation improvements: Added environment backup/restore mechanism in all-tests.sh:
  • Backs up and restores IDE_ROOT and PATH environment variables
  • Backs up and restores shell RC files (.bashrc, .zshrc) to prevent user configuration corruption
  • Resets test variables between each test execution using doResetVariables()
  • Added trap to ensure cleanup happens even on errors
• Improved error handling: Made the upgrade process more robust by continuing with downloaded version if upgrade fails
• Better function file detection: Added fallback logic to locate the functions file in both installation path and root directory
• New integration test: Added force-install.sh test to reproduce and validate the environment interference issue

These changes ensure that all integration tests succeed regardless of execution order, maintaining proper test independence.

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Checklist for this PR

Make sure everything is checked before merging this PR. For further info please also see
our DoD.

• 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

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Note: This PR replaces #1417 which was created by copilot-swe-agent. Due to CLA assistant issues with copilot-authored commits, the changes have been manually recreated with proper authorship attribution.

[coveralls]

Pull Request Test Coverage Report for Build 20335246277

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Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 70.088%

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Totals
Change from base Build 20334239472:	0.0%
Covered Lines:	10188
Relevant Lines:	13961

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💛 - Coveralls