fix: Boundary condition error in VerifyStream

[seebees]

Fixes: #507

Tests exist that push a single byte at a time.
This will hit every boundary condition.
However this is not complete enough.
State can be reset as the code transitions
from one boundary condition to another.

The prime example of this problem
the VerifyStream.
It has 4 boundary in the _transform function.
The body header, the body, the auth tag, and signature.
By sending 1 byte
as the code transitions from the body header
to the body
the code handling the exiting
of the body header has no way to interact
with the body,
because the 1 byte of data
completely isolates these code branches.

In this case the code was buffering
the body header in frameBuffer
but when exiting this section
and passing control to
the actual content section,
it used the chunk to form the tail.

When passing a single byte,
this tail would always be empty,
because it would have been incorporated
into the frame header.

Adding tests to span
the boundary conditions
to verify both this fix
and that there are not other lurking.

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