Add contains(), union(), length(), and empty() Array functions

[SteveL-MSFT]

PR Summary

Add contains(), union(), length(), and empty() array functions

I would suggest using the ARM docs for describing the behaviors which isn't completely obvious:
https://learn.microsoft.com/en-us/azure/azure-resource-manager/templates/template-functions-array#contains
https://learn.microsoft.com/en-us/azure/azure-resource-manager/templates/template-functions-array#union
https://learn.microsoft.com/en-us/azure/azure-resource-manager/templates/template-functions-array#length
https://learn.microsoft.com/en-us/azure/azure-resource-manager/templates/template-functions-array#empty

PR Context

Part of #976

[SteveL-MSFT]

Looks like length() and empty() are also Array functions, so will add those to this PR

[Copilot]

Pull Request Overview

This PR adds four new array functions to the DSC library: contains(), union(), length(), and empty(), which check for element existence, combine arrays/objects, return sizes, and check for emptiness respectively.

• Implementation of four new DSC array functions with comprehensive test coverage
• Registration of functions in the function dispatcher
• Addition of localized strings for error messages and descriptions

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
dsc_lib/src/functions/union.rs	Implements union function for merging arrays and objects
dsc_lib/src/functions/length.rs	Implements length function for arrays, objects, and strings
dsc_lib/src/functions/empty.rs	Implements empty function to check if collections are empty
dsc_lib/src/functions/contains.rs	Implements contains function for searching in collections
dsc_lib/src/functions/mod.rs	Registers the new functions in the function dispatcher
dsc_lib/locales/en-us.toml	Adds localized strings for the new functions
dsc/tests/dsc_functions.tests.ps1	Adds comprehensive test cases for all new functions

Comments suppressed due to low confidence (3)

dsc_lib/src/functions/contains.rs:98

• Use Value::Bool(true) instead of true for consistent type comparison in tests, matching the actual return type of the function.

        assert_eq!(result, true);

dsc_lib/src/functions/contains.rs:105

• Use Value::Bool(false) instead of false for consistent type comparison in tests, matching the actual return type of the function.

        assert_eq!(result, false);

dsc_lib/src/functions/contains.rs:112

• Use Value::Bool(true) instead of true for consistent type comparison in tests, matching the actual return type of the function.

        assert_eq!(result, true);