[CI] Run tests.yml more (#4943)

Namely:
 - When this workflow (`tests.yml`) is modified, it should be run
- When tests assets are modified, they should be run as well, otherwise
one can not really tell whether changes to the assets really do
anything, for example see CI (as screenshot below) run for
#4942)
<img width="611" alt="image"
src="https://github.com/pytorch/test-infra/assets/2453524/72aaf6aa-543f-4238-9f34-39d5b8bdd623">

.github/workflows/tests.yml

@@ -7,6 +7,8 @@ on:
       - '**.py'
       - '**requirements.txt'
       - .github/scripts/**
+      - tools/tests/assets/**
+      - .github/workflows/tests.yml
   push:
     branches:
       - main
@@ -15,6 +17,8 @@ on:
       - '**.py'
       - '**requirements.txt'
       - .github/scripts/**
+      - tools/tests/assets/**
+      - .github/workflows/tests.yml
 
 jobs:
   test-tools: