Adding support for VSCode command suffix's per extension

[vzhan00]

Description of changes:

Fixes duplicate command registration crash when multiple VS Code extensions (e.g., AWS Toolkit and CloudFormation standalone) run the same language server simultaneously.

Problem: vscode-languageclient registers commands from executeCommandProvider in VS Code's global command registry, which doesn't allow duplicates. The second extension to activate crashes with Error: command '/command/template/clear-diagnostic' already exists.

Fix: The server now derives a unique command suffix from initializationOptions.aws.clientInfo.extension.name (already sent by all clients). Each client gets uniquely-suffixed commands (e.g., /command/template/clear-diagnostic.aws.cloudformation), eliminating the collision.

Changes:

• ExecutionHandler.ts — createCommands(suffix) factory, module-level singleton with initCommands()/getCommands()
• LspCapabilities.ts — converted from static const to buildCapabilities(commands) function
• CodeActionService.ts — replaced hardcoded command strings with getCommands() calls
• standalone.ts — reads extension name from init params, calls initCommands()
• LspConnection.ts — updated default handler to use buildCapabilities()

Backward compatible: If no extension name is provided, commands remain unsuffixed (original behavior). Currently since we're using the extension name, the existing toolkit suffix will be amazonwebservices.aws-toolkit-vscode and for the standalone it will be aws.cloudformation.

Testing:

• 3328 unit tests pass
• Manually verified both Toolkit and standalone extension running simultaneously without crash
• Verified code actions fire correctly with suffixed commands

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[satyakigh]

We should only allow this if its a string, otherwise throw

[satyakigh]

Instead of this singleton pattern, can the suffix be used to directly create LspCapabilities + LspConnection. Then just send the capabilities which has the set of commands directly to CfnServer creation and pass the commands down to execution handler and code action handler?