Store member keys in compressed form to lower the size of CommunityDescription

[osmaczko]

          If a refactor is going to be done for community members, please do include the following:

Community members are stored like this in the community description:

map<string,CommunityMember> members = 2;

with the string key containing a 130char string with the member public key ("0x" + 128 hex characters). We should use instead the 33 bytes compressed version with no "0x" prefix to save space.

Originally posted by @richard-ramos in status-im/status-desktop#12188 (comment)