Add tryGet() function

[SteveL-MSFT]

PR Summary

Add the tryGet() function as defined by ARM

PR Context

Fix #1180

[Copilot]

Pull Request Overview

This PR implements the tryGet() function as defined by ARM to safely retrieve values from arrays and objects without throwing errors when keys or indices don't exist.

• Adds a new tryGet() function that returns null for non-existent keys/indices instead of failing
• Supports both object property access by string key and array element access by numeric index
• Includes comprehensive test coverage for both positive and negative scenarios

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
lib/dsc-lib/src/functions/try_get.rs	Implements the complete tryGet function with object/array access logic and unit tests
lib/dsc-lib/src/functions/mod.rs	Registers the new tryGet function in the function dispatcher
lib/dsc-lib/locales/en-us.toml	Adds localized strings for function description and error messages
dsc/tests/dsc_functions.tests.ps1	Adds integration tests covering various tryGet usage scenarios

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