Fix: Un-escape the value before setting LANG

[Feng Wang (chemwolf6922)]

Summary of the Pull Request

The value in locale files could be shell escaped. The old parsing logic sets the string directly. Which could set LANG to a wrong value like "en_US.UTF-8".

This PR un-escapes the value string before setting it to the env LANG.

PR Checklist

• Closes: Cannot run PowerShell 7.7.0 Preview 2 on AlmaLinux 8 with WSL 2.9.4.0 #41090
• 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

Update tests:
SimpleTests::SimpleTests::StringHelpers
UnitTests::UnitTests::ConfigUpdateLanguage

[Copilot]

Pull request overview

This PR fixes incorrect LANG values when distro locale files store the value with shell-style escaping/quoting (e.g., LANG="en_US.UTF-8"). It adds shared string helpers to trim and unescape shell-escaped strings, then uses them when parsing locale configuration in the Linux init path, with accompanying unit test updates.

Changes:

• Add wsl::shared::string::Trim() and wsl::shared::string::UnescapeShell() helpers in stringshared.h.
• Unescape/trim the locale-file LANG value before calling Environment.AddVariable() in src/linux/init/config.cpp.
• Update/extend unit tests to cover quoted locale values and new string helper behavior.

Reviewed changes

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

File	Description
test/windows/UnitTests.cpp	Adjusts language config test to validate quoted LANG values using printenv.
test/windows/SimpleTests.cpp	Adds coverage for new Trim/UnescapeShell helpers.
src/shared/inc/stringshared.h	Introduces Trim and UnescapeShell utilities for shared string handling.
src/linux/init/config.cpp	Applies trim + shell-unescape to locale-file LANG prior to setting the environment.