Add --ignore-settings-file and DSC_IGNORE_SETTINGS_FILE env var

[SteveL-MSFT]

PR Summary

Partner has a need to ignore the settings file. Added --ignore-settings-file switch but can also set DSC_IGNORE_SETTINGS_FILE env var (just has to exist, value doesn't matter) for the same purpose. We can consider adding a setting to the file to now allow this switch should that need arise.

The implementation simply sets the env var if the switch is used.

[Copilot]

Pull request overview

Adds a new way to bypass DSC settings-file processing by introducing a --ignore-settings-file CLI switch and a DSC_IGNORE_SETTINGS_FILE environment variable, primarily to support partner scenarios where settings-file behavior must be suppressed.

Changes:

• Introduces --ignore-settings-file (and wires it to set DSC_IGNORE_SETTINGS_FILE) to disable settings-file usage.
• Updates dsc-lib settings resolution to short-circuit when the env var is present and emits a warning.
• Adds Pester coverage validating both the env var and CLI flag behaviors, plus localized help/warning strings.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
lib/dsc-lib/src/util.rs	Adds env var gate to skip settings lookup and warn.
lib/dsc-lib/locales/en-us.toml	Adds localized warning text for ignoring the settings file.
dsc/tests/dsc_settings.tests.ps1	Adds tests for env var and CLI flag behavior.
dsc/src/main.rs	Sets DSC_IGNORE_SETTINGS_FILE when --ignore-settings-file is used.
dsc/src/args.rs	Adds --ignore-settings-file argument definition.
dsc/locales/en-us.toml	Adds localized help text for the new CLI flag.