Correctly handle empty arguments when creating processes

[OneBlue]

Summary of the Pull Request

This change updates the init protocol to correctly handle empty strings in array.

This change also test coverage for empty arguments at the VM, container and exec level

PR Checklist

• Closes: Link to issue #xxx
• Communication: I've discussed this with core contributors already. If work hasn't been agreed, this work might be rejected
• Tests: Added/updated if needed and all pass
• Localization: All end user facing strings can be localized
• Dev docs: Added/updated if needed
• Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

Validation Steps Performed

[Copilot]

Pull request overview

This PR fixes the handling of empty string arguments when creating processes in WSL by updating the init protocol. Previously, the protocol couldn't distinguish between empty strings and the end of the array because it used null-terminated strings. The new protocol uses length-prefixed strings with an int32_t size prefix for each string and a -1 terminator for the array.

Changes:

• Updated string array serialization to use length-prefixed format instead of null-terminated format
• Updated string array deserialization to handle the new format and return vector<string> instead of vector<const char*>
• Added comprehensive test coverage for empty arguments at VM, container, and exec levels

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/shared/inc/message.h	Updated WriteStringArray to serialize strings with int32_t length prefix and -1 terminator
src/shared/inc/stringshared.h	Updated ArrayFromSpan to deserialize length-prefixed strings into vector<string>; added StringPointersFromArray helper
src/shared/inc/prettyprintshared.h	Updated pretty printing to use new ArrayFromSpan API and added MessageSize field to StringArray struct
src/linux/init/WSLAInit.cpp	Updated to use StringPointersFromArray to convert string vectors to char pointer arrays for execve
test/windows/WSLATests.cpp	Added tests validating empty argument handling for VM processes, container init processes, and exec'd processes