WEBTRANSPORT -> WT in most places. Only ENABLE_WEBTRANSPORT
remains (since it is a draft-02 setting that was later removed)
as well as internal functions and atoms about stream headers,
for greater clarity.

This adds support for WebTransport HTTP/3 settings, error codes,
headers, stream types as well as capsules, with an initial
implementation of the Capsule protocol.

This allows cleaning up timers and avoids receiving
stray timeout messages when reusing a process. This
is otherwise optional since the termination of a
process cleans up the timers.

This is to be used primarily by a client before initiating a new stream
so that it can respect the setting from the server.

When the client does not provide the "client_max_window_bits" option,
the server must be able to handle a sliding window of up to 32,768 bytes.

When the server has configured a lower limit than the default, and the
client has not provided the parameter, compression must be disabled.

Co-authored-by: Ignacio Martínez <ignacio.martinez.rivera@gmail.com>

The `max_inflate_size` value can be configured in the extensions
map to set a limit to the size of the expanded data.

This is done via the previously introduced cow_deflate:inflate/3
function.