Include relevant values in ReadBuf.put_slice() panic message

[OmegaJak]

Is your feature request related to a problem? Please describe.
A service I work on panicked due to the assert at the top of io::ReadBuf::put_slice(), however, the panic message did not include the values that were compared, which would help with debugging the problem.

Describe the solution you'd like
If calling put_slice() panics as a result the remaining space in the ReadBuf being less than the slice's length, it would be nice for the panic message to include the values of self.remaining() and buf.len(). This is the assert in question. I would propose updating it to something like

assert!(
    self.remaining() >= buf.len(),
    "buf.len() must fit in remaining(); buf.len() = {}, remaining() = {}",
    buf.len(),
    self.remaining()
);

Describe alternatives you've considered
Additional logging of these values can be done by users of this function. I suppose it could also return a Result with an error that contains the mismatch but that's a much bigger change that probably has its own downsides.

Additional context
There does seem to be a number of these asserts scattered around tokio and I couldn't find any that included the errant values in the message for a greater than/less than check. If including the values in the error message is a desirable behavior, then it may be worth thinking about adding/using assert macros like assert_eq! for the various greater than/less than comparisons (assert_ge!, assert_le!, etc).

[Darksonn]

This seems like a good idea.