Do not remove envs which are provided by the consumer (microsoft#20424)

For microsoft#20292

We currently remove environments from cache which aren't part of the
latest discovery run. This is not correct as consumers can still select
envs not reported by discovery run, which we shouldn't remove.

Author: Kartik Raj

src/client/pythonEnvironments/base/locators/composite/envsCollectionCache.ts

@@ -99,15 +99,20 @@ export class PythonEnvInfoCache extends PythonEnvsWatcher<PythonEnvCollectionCha
                     if (envs && isCompleteList) {
                         /**
                          * Only consider a cached env to be valid if it's relevant. That means:
-                         * * It is either reported in the latest complete refresh for this session.
-                         * * Or it is relevant for some other workspace folder which is not opened currently.
+                         * * It is relevant for some other workspace folder which is not opened currently.
+                         * * It is either reported in the latest complete discovery for this session.
+                         * * It is provided by the consumer themselves.
                          */
                         if (cachedEnv.searchLocation) {
                             return true;
                         }
                         if (envs.some((env) => cachedEnv.id === env.id)) {
                             return true;
                         }
+                        if (Array.from(this.validatedEnvs.keys()).some((envId) => cachedEnv.id === envId)) {
+                            // These envs are provided by the consumer themselves, consider them valid.
+                            return true;
+                        }
                     } else {
                         return true;
                     }
@@ -141,7 +146,7 @@ export class PythonEnvInfoCache extends PythonEnvsWatcher<PythonEnvCollectionCha
     public addEnv(env: PythonEnvInfo, hasLatestInfo?: boolean): void {
         const found = this.envs.find((e) => areSameEnv(e, env));
         if (hasLatestInfo) {
-            traceVerbose(`Adding env to cache ${env.id}`);
+            traceVerbose(`Flushing env to cache ${env.id}`);
             this.validatedEnvs.add(env.id!);
             this.flush(env).ignoreErrors(); // If we have latest info, flush it so it can be saved.
         }