Support environment variables in config.xml

[gregg-miskelly]

This PR adds support for an Environment dictionary in config.xml to make it easy to configure cygwin tests on Windows.

[Copilot]

Pull request overview

This PR extends the CppTests configuration pipeline to allow a <Environment> block in config.xml to define additional environment variables that will be applied when launching the debug adapter (useful for Windows MSYS/Cygwin-style setups that need PATH tweaking).

Changes:

• Added an EnvironmentVariables dictionary to IDebuggerSettings and propagated it through TestSettings/DebuggerSettings.
• Implemented parsing of a new <Environment> element in TestSettingsHelper and wired it into debug adapter process launch via DebugAdapterRunner.
• Updated the MSYS GDB sample configuration to include an (optional) <Environment> section.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
test/DebuggerTesting/IDebuggerSettings.cs	Adds EnvironmentVariables to the debugger settings contract.
test/DebuggerTesting/Attribution/TestSettingsHelper.cs	Parses <Environment> from config.xml into a dictionary.
test/DebuggerTesting/Attribution/TestSettings.cs	Propagates environment variables into DebuggerSettings.
test/DebuggerTesting/Attribution/DebuggerSettings.cs	Stores EnvironmentVariables on DebuggerSettings.
test/CppTests/TestConfigurations/config_msys_gdb.xml	Adds an example <Environment> section for MSYS GDB.
test/CppTests/OpenDebug/CrossPlatCpp/DebuggerRunner.cs	Passes environment variables to DebugAdapterRunner when starting the adapter.