Add Wireshark support for XATTR binary protocol changes

Add support to the Couchbase Wireshark dissector for the new binary protocol changes for XATTRs.

This includes:

• Changes to subdoc for reading/writing XATTRs
• Addition of HELLO::XATTR flag
• Changes to SET_WITH_META (datatype) to support including XATTRs
• Changes to DCP MUTATION / DELETION to support decoding XATTRs.

Previous commits to wireshark by Couchbase:

• https://code.wireshark.org/review/#/c/10151/
• https://code.wireshark.org/review/#/c/13688/
• https://code.wireshark.org/review/#/c/14004/