Resolve shell env API performance issue for single env approach

[anthonykim1]

Potential root of the performance cause:

1. Using diff approach where we check for change the environment variables, and only firing an event if there is a difference, should resolve the problem
2. O(n) - iterating through each environment variable in the process of fetching them (inside shell such as bash) is what is slow
3. Print statements in the above O(n) is what is causing the slowness (shell side: e.g. bash side)
4. O(n) - iterating through each environment variable when trying to calculate the diff is what is slow (in the shellEnvDetectionCapability)

Edit: d3ef701 brought back instant bash prompts. I think it was combination of printenv with compgen and tons of printf statements really slowing things down. So Mainly Scenario number 3 was correct

[anthonykim1]

https://github.com/user-attachments/assets/57167cc9-fd5b-424b-b302-83542592365d
@Tyriar This is for bash, but I think I brought back the perf to normal

[anthonykim1]

TODO: Should address #238338 (comment) if we were to enable shell env for bash again since it is critical.