Revert "Optimize various aggregate deserialization functions"
This reverts commit
608fd198def5390c3490bfe903730207dfd8eeb4.
On 2nd thoughts, the StringInfo API requires that strings are NUL
terminated and pointing directly to the data in a bytea Datum isn't NUL
terminated.
Discussion: https://postgr.es/m/CAApHDvorfO3iBZ=xpiZvp3uHtJVLyFaPBSvcAhAq2HPLnaNSwQ@mail.gmail.com