enhance linters configuration and improve code readability

[mmorel-35]

This introduces several improvements and code quality enhancements across the codebase, including updates to linter configuration, refactoring for clarity and maintainability, and minor bug fixes. The most significant changes are grouped below.

Linter and Code Quality Enhancements:

• .golangci.yml: Enabled additional linters (gocritic, modernize, revive) and configured their rules to catch more code issues and enforce consistent style. Also, set max-issues-per-linter and max-same-issues to 0 to report all issues.
• Refactored several test and function signatures to use blank identifiers for unused parameters, improving code clarity and linter compliance .

Code Refactoring and Simplification:

• user/idtools_unix.go: Refactored variable assignments to use short variable declarations for error handling, improving readability and preventing potential variable shadowing issues.
• user/idtools_unix.go: Simplified increment operation in lookupSubRangesFile for clarity.

Bug Fixes and Test Improvements:

• capability/capability_linux.go: Replaced if/else chains with a switch statement in mkString for improved logic clarity.
• capability/capability_test.go: Improved empty string check for bounding set in tests.
• mount/sharedsubtree_linux_test.go: Removed unnecessary deferred function in TestSubtreeUnbindable for cleanup, streamlining test logic.

Minor Corrections and Consistency Improvements:

• signal/signal.go: Renamed a variable from signal to sig to avoid shadowing and improve code clarity.
• mount/mounter_linux_test.go: Updated function signature for validateMount to use a more concise parameter list.
• mountinfo/mounted_linux_test.go Improved test logic for bind mount detection and error handling.

[Copilot]

Pull request overview

This PR tightens Go linting and performs small refactors across runtime code and tests to improve readability and linter compliance.

Changes:

• Expanded .golangci.yml to enable additional linters and report all issues.
• Refactored Go code and tests for clearer variable usage (avoiding shadowing / unused params) and minor readability improvements.
• Simplified a few test/control-flow snippets (e.g., switch in capability string formatting, minor test cleanup).

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
.golangci.yml	Enables gocritic, modernize, revive, and configures issue reporting limits.
user/idtools_unix.go	Uses short declarations for error checks and simplifies an increment.
signal/signal.go	Renames local variable to avoid shadowing (signal → sig).
reexec/reexec_test.go	Uses blank identifier for an unused test callback parameter.
mountinfo/mounted_linux_test.go	Tweaks test logic around bind-mount detection expectations.
mount/sharedsubtree_linux_test.go	Removes an unnecessary deferred unmount in a test.
mount/mounter_linux_test.go	Makes a helper function signature more concise.
devices/device_unix_test.go	Uses blank identifiers for unused stub parameters in tests.
capability/capability_test.go	Uses a direct empty-string check for the bounding set assertion.
capability/capability_linux.go	Replaces an if/else chain with a switch for clarity.

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[Copilot]

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated no new comments.