Complete resource delete plumbing

[tgauth]

PR Summary

• add --what-if and --output-format args to dsc resource delete command

[Copilot]

Pull request overview

Adds --what-if support to the dsc resource delete CLI flow, wiring the flag from argument parsing through subcommand dispatch into the resource invocation layer, and validating behavior with a new PowerShell test.

Changes:

• Add --what-if (and -w) to dsc resource delete and plumb it through to resource.delete(..., ExecutionKind::WhatIf).
• Add delete-command output formatting support and emit structured output for delete what-if results.
• Add a Pester test asserting dsc resource delete --what-if returns delete what-if metadata.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
dsc/tests/dsc_whatif.tests.ps1	Adds a Pester test validating dsc resource delete --what-if output contains delete what-if messages.
dsc/src/args.rs	Extends resource delete CLI args with --what-if and --output-format.
dsc/src/subcommand.rs	Plumbs new delete args into the resource_command::delete call.
dsc/src/resource_command.rs	Implements what-if execution kind for delete and prints structured output for what-if results.

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[SteveL-MSFT]

@tgauth can you fix the merge conflict?