XWIKI-19270: Add support for performing the PDF export using a browser running...

XWIKI-19270: Add support for performing the PDF export using a browser running in a Docker container
* Read smaller chunks from the PDF "stream" in order to avoid a BufferOverflow exception raised by the Tyrus (WebSocket) client used to communicate with the headless Chrome browser.

(cherry picked from commit 85ff7df0)