Apply custom env variables to terminal when in pythonTerminalEnvVarActivation experiment (microsoft#21879)

For microsoft#944 microsoft#20822 

We only apply those env vars to terminal which are not in process env
variables, hence remove custom env vars from process variables.

Author: Kartik Raj

src/client/common/process/processFactory.ts

@@ -17,8 +17,10 @@ export class ProcessServiceFactory implements IProcessServiceFactory {
         @inject(IProcessLogger) private readonly processLogger: IProcessLogger,
         @inject(IDisposableRegistry) private readonly disposableRegistry: IDisposableRegistry,
     ) {}
-    public async create(resource?: Uri): Promise<IProcessService> {
-        const customEnvVars = await this.envVarsService.getEnvironmentVariables(resource);
+    public async create(resource?: Uri, options?: { doNotUseCustomEnvs: boolean }): Promise<IProcessService> {
+        const customEnvVars = options?.doNotUseCustomEnvs
+            ? undefined
+            : await this.envVarsService.getEnvironmentVariables(resource);
         const proc: IProcessService = new ProcessService(customEnvVars);
         this.disposableRegistry.push(proc);
         return proc.on('exec', this.processLogger.logProcess.bind(this.processLogger));

src/client/common/process/types.ts

@@ -55,7 +55,7 @@ export interface IProcessService extends IDisposable {
 export const IProcessServiceFactory = Symbol('IProcessServiceFactory');
 
 export interface IProcessServiceFactory {
-    create(resource?: Uri): Promise<IProcessService>;
+    create(resource?: Uri, options?: { doNotUseCustomEnvs: boolean }): Promise<IProcessService>;
 }
 
 export const IPythonExecutionFactory = Symbol('IPythonExecutionFactory');

src/client/interpreter/activation/service.ts

@@ -192,7 +192,7 @@ export class EnvironmentActivationService implements IEnvironmentActivationServi
                 args[i] = arg.toCommandArgumentForPythonExt();
             });
             const command = `${interpreterPath} ${args.join(' ')}`;
-            const processService = await this.processServiceFactory.create(resource);
+            const processService = await this.processServiceFactory.create(resource, { doNotUseCustomEnvs: true });
             const result = await processService.shellExec(command, {
                 shell,
                 timeout: ENVIRONMENT_TIMEOUT,