Simplify the autoinc initialization code. This removes the
non-determinism related to reading the table's autoinc value for the first
time. This change has also reduced the sizeof dict_table_t by sizeof(ibool)
bytes because we don't need the dict_table_t::autoinc_inited field anymore.

Bug#39830 Table autoinc value not updated on first insert.
Bug#35498 Cannot get table test/table1 auto-inccounter value in ::info
Bug#36411 Failed to read auto-increment value from storage engine" in 5.1.24 auto-inc
rb://16