Add endsWith, startsWith, utcNow, and uniqueString functions

[SteveL-MSFT]

PR Summary

Add endsWith(), startsWith(), utcNow(), and uniqueString() functions. Note that utcNow() supports a subset of the .NET datetime formatting strings.

Also refactored how functions get registered with DSC so that it's from a vector and takes the name from the metadata so no risk of them being out of sync.

PR Context

Part of #976

[Copilot]

Pull Request Overview

This PR adds four new string and date functions to the DSC library: endsWith, startsWith, utcNow, and uniqueString. These functions enhance the DSC template expression capabilities with string manipulation and utility operations.

• Implements string prefix/suffix checking with startsWith and endsWith functions
• Adds utcNow function for date formatting with .NET format string conversion support
• Provides uniqueString function for generating deterministic hashes from concatenated inputs
• Refactors function registration from individual insertions to a vector-based approach for better maintainability

Reviewed Changes

Copilot reviewed 10 out of 13 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
dsc_lib/src/functions/ends_with.rs	New function to check if a string ends with a specified suffix
dsc_lib/src/functions/starts_with.rs	New function to check if a string starts with a specified prefix
dsc_lib/src/functions/utc_now.rs	New function to get current UTC time with optional .NET format string support
dsc_lib/src/functions/unique_string.rs	New function to generate deterministic unique strings from input arguments
dsc_lib/src/functions/mod.rs	Refactored function registration and added new function imports
dsc_lib/src/configure/context.rs	Added parameter default processing flag to context
dsc_lib/src/configure/mod.rs	Updated parameter default processing to use context flag
dsc_lib/locales/en-us.toml	Added localization strings for new functions
dsc_lib/Cargo.toml	Added dependencies for new functions (base32, murmurhash64)
dsc/tests/dsc_functions.tests.ps1	Added comprehensive tests for new functions

[tgauth]

LGTM