Support receiving fragmented STOMP frames

Support receiving STOMP frame split into multiple Websocket
messages, since this is the current behavior of Stomp.js and
Dart STOMP library when frames are bigger than 16 Kbytes.

This commit also introduces a new maxFrameBufferSize parameter
(default 64 Kbytes) in order to allow to configure the maximum
size of a whole STOMP frame (fragmented or not).

Issue: SPR-11527