Changed title: migrate TIMESTAMP to DATETIMEs to support dates past 2038?

For native MariaDB 10.5.8, MySqlLeaseMgrTest.maxDate* tests pass.

When starting MariaDB 10.5.8 in docker with this script, they fail:

$ ./src/lib/dhcpsrv/tests/libdhcpsrv_unittests --gtest_filter='MySqlLeaseMgrTest.maxDate*'

Note: Google Test filter = MySqlLeaseMgrTest.maxDate*
[==========] Running 4 tests from 1 test suite.
[----------] Global test environment set-up.
[----------] 4 tests from MySqlLeaseMgrTest
[ RUN      ] MySqlLeaseMgrTest.maxDate4
wipeMySQLData failed:[sh /home/andrei/work/isc/kea/src/share/database/scripts/mysql/wipe_data.sh 9.5 -N -B --user=keatest --password=keatest keatest 2>/dev/null ]
test_utils.cc:54: Failure
Expected equality of these values:
  first->cltt_
    Which is: 2147483647
  second->cltt_
    Which is: 1610629470
[  FAILED  ] MySqlLeaseMgrTest.maxDate4 (1679 ms)
[ RUN      ] MySqlLeaseMgrTest.maxDate4MultiThreading
test_utils.cc:54: Failure
Expected equality of these values:
  first->cltt_
    Which is: 2147483647
  second->cltt_
    Which is: 1610629470
[  FAILED  ] MySqlLeaseMgrTest.maxDate4MultiThreading (56 ms)
[ RUN      ] MySqlLeaseMgrTest.maxDate6
test_utils.cc:87: Failure
Expected equality of these values:
  first->cltt_
    Which is: 2147483647
  second->cltt_
    Which is: 1610629470
[  FAILED  ] MySqlLeaseMgrTest.maxDate6 (56 ms)
[ RUN      ] MySqlLeaseMgrTest.maxDate6MultiThreading
test_utils.cc:87: Failure
Expected equality of these values:
  first->cltt_
    Which is: 2147483647
  second->cltt_
    Which is: 1610629470
[  FAILED  ] MySqlLeaseMgrTest.maxDate6MultiThreading (56 ms)
[----------] 4 tests from MySqlLeaseMgrTest (1847 ms total)
[----------] Global test environment tear-down
[==========] 4 tests from 1 test suite ran. (1847 ms total)
[  PASSED  ] 0 tests.
[  FAILED  ] 4 tests, listed below:
[  FAILED  ] MySqlLeaseMgrTest.maxDate4
[  FAILED  ] MySqlLeaseMgrTest.maxDate4MultiThreading
[  FAILED  ] MySqlLeaseMgrTest.maxDate6
[  FAILED  ] MySqlLeaseMgrTest.maxDate6MultiThreading
4 FAILED TESTS

The date that is returned is the current time. When looking into the database, the date that is inserted inside the test is MAX_DATE. When doing a manual select via mysql client, it is MAX_DATE. So the problem must be on the SELECT statement when using the MySQL libs which were the same version when I tested mariadb-libs 10.5.8.