Equality: less automatic simplification and fix 'Eq(p, 0)' for p positive

update: no longer on top of #7959 and #7838.
How about:

```
Note: do not attempt simplification to prove that this is zero. 
If the user wants this, they can use the simplify function
on the unevaluated Equality.
```

And a test you can add is the one that I gave before:

```
Eq(cos(x)**2 + sin(x)**2, 1) != True
```

I'm not sure if anyone has a preference in where to put the note: with the test that might fail or in the code. I *think* I prefer the code since someone changing things is more likely to see it there. If they make the change and see that a test fails then they will read the test note...and wish that someone had put it in the code.