Problem:
========
During checkpoint, we are writing all MLOG_FILE_NAME records in one mtr
and parse buffer can't be processed till MLOG_MULTI_REC_END. Eventually parse
buffer exceeds the RECV_PARSING_BUF_SIZE and eventually it overflows.

Fix:
===
1) Break the large mtr if it exceeds LOG_CHECKPOINT_FREE_PER_THREAD into multiple mtr during checkpoint.
2) Move the parsing buffer if we are encountering only MLOG_FILE_NAME
records. So that it will never exceed the RECV_PARSING_BUF_SIZE.
Reviewed-by: Debarun Bannerjee <debarun.bannerjee@oracle.com>
Reviewed-by: Rahul M Malik <rahul.m.malik@oracle.com>
RB: 14743