FastSerializer: Remove throw specs; this is not UNO implementation

Change-Id: I462f8ed89de48174ed7aa6e008709963bec50649
FastSerializer: Use FastAttributeList directly to write faster.

Change-Id: I28085d4e060bcf052e6aa97a0822a4d653d7c066
FastSerializer: avoid some more OStrings

Change-Id: I2d5dbe9adccdd231cc16a1f83a90a4adeb965c64