[Optimization] Lack of interruption function during generation process when uising TypeSpec VS Code Extension

[jianingwang123]

Description:
When using the TypeSpec VS Code Extension, there is a lack of interruption functionality during the generation process. If I mistakenly select an unwanted language or other options, I cannot cancel midway and have to wait for the generation process to complete automatically.

Repro steps:

1. Install the typespec extension.
2. Install @typespec/compiler: npm install -g @typespec/compiler.
3. Typing >TypeSpec: Generate from TypeSpec and Click the command.
4. Choose a project.
5. Select Emitter Type.
6. Select a language, mistakenly select an unwanted language.
7. Have to wait for the generation process to complete automatically.

Environment:

• TypeSpec VS Code Extension version: 0.64.0
• TypeSpec compiler/CLI version: 0.64.0
• OS: Windows, Linux

Expected behavior:
Users can interrupt the generation process themselves during the generation.

@RodgeFu, @msyyc and @chunyu3 for notification.