In a similar fashion to what have been done with `fill_from_stream`,
this new method allows to write CircularBuffer's data to a Stream
without additional copies.
Instead of reading bytes from the output stream into a buffer, just to
immediately write them back out, we can skip the middle-man and copy the
bytes directly into the output buffer.
When reading, we currently only fill a BufferedStream's buffer when it
is empty, and only with 1 KB of data. This means that while the buffer
defaults to a size of 16 KB, at least 15 KB is always unused.
This parameter allows to start searching after an offset. For example,
to resume a search.
It is unfortunately a breaking change in API so this patch also modifies
one user and one test.
The previously defined operator was swap-based. With the defaulted
implementation, both integers are now copied, but it doesn't matter as
only the `ByteBuffer` allocates memory (i.e. non-null integers values
won't affect the destruction).
The class is very similar to `CircularDuplexStream` in its behavior.
Main differences are that `CircularBuffer`:
- does not inherit from `AK::Stream`
- uses `ErrorOr` for its API
- is heap allocated (and OOM-Safe)
This patch also add some tests.
