SDK / exoplayer

The assertion about the expected formats doesn't really belong in a
fake, the assertions should be closer to the test method.

This gets in the way when I try and write a new test in
AnalyticsCollectorTest that doesn't use the expected, constant Format
(because i want to specify drmInitData) - but changing the expected
Format is tricky because it's hard-coded into the FakeVideoRenderer
inner class.

I replaced the assertion in FakeRenderer with assertions in test
methods that used to assert on the format count.

PiperOrigin-RevId: 301353072