hotfix: QueryNode handling of membership handle

[mnaamani]

Problem:
If member handle has non-valid utf-8 chars and is replaced with the � replacement character, two unique (at byte level) handles when converted to string can actually become identical, breaking the uniqueness constraint in the database for the handle column.

Solution:
Update query-node schema to:

• do best effort converting handle to utf-8 string an store it in non-unique column
• store raw bytes as hex string in new column

[zeeshanakram3]

LGTM

[ignazio-bovo]

LGTM

[ignazio-bovo]

ok