CREATE TABLE ... IGNORE SELECT statement didn't properly cleanup
TABLE::auto_increment_field_not_null member in cases when last row
to be inserted was skipped due to failing CHECK constraint.
As result next statement using the same table might have failed
on assertion. The problem affected debug builds only.

The problem was caused by missing cleanup of this member in the
code path that handled CHECK constraint failure in CREATE TABLE
... SELECT.

Bug#30126375 "LOAD DATA WITH SET CLAUSE IGNORES NO_AUTO_VALUE_ON_ZERO MODE".

LOAD DATA with SET clause generated new value for auto-increment field
instead of using 0 value provided in the file even in NO_AUTO_VALUE_ON_ZERO
mode.

This problem was caused by incorrect handling of auto_increment_field_not_null
flag as well. Code which processed LOAD DATA's SET clause called fill_record()
function which wrongly reset this flag, even though it was earlier properly set
by code loading values from a file. As result 0 coming from the file was
treated as default, causing new auto-increment generation.

This patch solves these two problems by changing the way fill_record()
calls handle TABLE::auto_increment_field_not_null flag and how resetting
of this flag after calls to fill_record() is done.

Specifically:
  - We no longer reset TABLE::auto_increment_field_not_null at the start
    of fill_record(). Instead we rely on the fact that this flag is reset
    for TABLE objects which are new or come from Table Cache. We also
    rely on the fact this flag will be correctly reset before call to
    fill_record() processing next row. This step solves the second bug
    mentioned above.
  - We enforce the latter, and the fact that this flag is correctly
    reset in all cases when we finish row processing by using newly
    introduced RAII class instead of relying on manual cleanup.
    This step solves the first bug mentioned above.
  - Also to avoid  RAII object use in cases when we call fill_record() but
    don't really need value of TABLE::auto_increment_field_not_null (e.g.
    in UPDATE implementation), new argument was added to fill_record()
    to skip raising of this flag.
  - Finally, TABLE::auto_increment_field_not_null flag was renamed to
    better reflect the fact that it actually means that there is explicit
    non-NULL value for the auto-increment field.

Reviewed-by: Sivert Sorumgaard <sivert.sorumgaard@oracle.com>