Buffer zero init test for binding (and use in a compute shader)

[Wumpf]

Connections
Buffer zero init #1159
Buffer zero crash on unused buffer fix #1190

Description
Tried to create a player ron file repro case for #1190 but didn't work out quite well (test keeps buffers alive even when I tried to go through an indirection via buffer copies). But with a bit of cleanup the test still felt very useful since it gives more coverage to buffer zero init.

Generally zero init is hard to test since the way to get the result is to map it which is one particular case of requiring zero init. But there's a few ways like in this test here where we look at what modifications a compute shader did to a buffer - since the buffer was not explicitly initialized, the outcome would be different if the compute shader would have seen a buffer without zero init.

Given how few tests there are right now this ofc implicitly tests a bunch of other things ;)

[monocodus]

This is an autogenerated code review.

Checker summary (by rust_clippy):
The tool has found 94 warnings, 0 errors.

[kvark]

Also filed #1195 to make our RON captures nicer.

[monocodus]

This is an autogenerated code review.

Checker summary (by rust_clippy):
The tool has found 94 warnings, 0 errors.

[kvark]

Thank you!
bors r+

[bors]

Build succeeded:

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