Revamp the QRF insert-mode optimization of [659ff6ab55802507]. The

Revamp the QRF insert-mode optimization of [659ff6ab55802507].  The
control value is now nMultiInsert.  Multiple rows are added to each INSERT
statement until the number of bytes in that statement exceeds the
nMultiInsert value.  The CLI uses a default value of 3000, which provides
a good balance between speed and prepare-statement size.  The output
from ".dump" now loads nearly 2x faster in some cases.

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