Add sample Service Template for Porch pod functions and add E2E Tests for same

[gkumar78]

Noticed that there is no E2E test which is using function pod template configmap. Hence, when manual test was executed with sample function pod template configmap without serviceTemplate attribute, the test failed.

Need to enrich function pod template configmap with serviceTemplate attribute and also add E2E Testcase using the same.

[gkumar78]

Submitted 2 PRs for this issue

Porch repo - nephio-project/porch#285
Docs repo - nephio-project/docs#249

[gkumar78]

Both PRs for this issue are merged