Pre-fill resource group name with environment name in container apps environment creation flow

[Copilot]

When creating a new container apps environment and selecting "+ Create new resource group", the resource group name input was blank instead of being pre-populated with the environment name.

Root cause

ResourceGroupNameStep (from vscode-azext-azureutils) uses wizardContext.relatedNameTask as the suggested default value for its input box. ManagedEnvironmentNameStep never populated this task, so the field was always empty.

Change

Set relatedNameTask in ManagedEnvironmentNameStep.prompt() after the user enters the environment name:

context.relatedNameTask ??= Promise.resolve(context.newManagedEnvironmentName);

Uses ??= to avoid overwriting if already set by a prior step. The resource group name input box now pre-fills with the environment name, matching the behavior of the standalone createManagedEnvironment command where the resource group name is always set to match the environment name.