[BEHAVIOR] Add ability to choose between DATETIME and TIMESTAMP

[wollanup]

Closes https://github.com/propelorm/Propel2/issues/1971

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (4f36eea) 89.27% compared to head (85745f9) 89.27%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1978 +/- ## ========================================= Coverage 89.27% 89.27% - Complexity 8049 8052 +3 ========================================= Files 232 232 Lines 24519 24521 +2 ========================================= + Hits 21889 21891 +2 Misses 2630 2630 ``` | [Flag](https://app.codecov.io/gh/propelorm/Propel2/pull/1978/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=propelorm) | Coverage Δ | | |---|---|---| | [5-max](https://app.codecov.io/gh/propelorm/Propel2/pull/1978/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=propelorm) | `89.27% <100.00%> (+<0.01%)` | :arrow_up: | | [7.4](https://app.codecov.io/gh/propelorm/Propel2/pull/1978/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=propelorm) | `89.27% <100.00%> (+<0.01%)` | :arrow_up: | | [agnostic](https://app.codecov.io/gh/propelorm/Propel2/pull/1978/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=propelorm) | `67.47% <100.00%> (+<0.01%)` | :arrow_up: | | [mysql](https://app.codecov.io/gh/propelorm/Propel2/pull/1978/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=propelorm) | `69.84% <100.00%> (+0.03%)` | :arrow_up: | | [pgsql](https://app.codecov.io/gh/propelorm/Propel2/pull/1978/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=propelorm) | `69.87% <100.00%> (+0.03%)` | :arrow_up: | | [sqlite](https://app.codecov.io/gh/propelorm/Propel2/pull/1978/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=propelorm) | `67.81% <100.00%> (+0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=propelorm#carryforward-flags-in-the-pull-request-comment) to find out more. | [Files Changed](https://app.codecov.io/gh/propelorm/Propel2/pull/1978?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=propelorm) | Coverage Δ | | |---|---|---| | [...r/Behavior/Timestampable/TimestampableBehavior.php](https://app.codecov.io/gh/propelorm/Propel2/pull/1978?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=propelorm#diff-c3JjL1Byb3BlbC9HZW5lcmF0b3IvQmVoYXZpb3IvVGltZXN0YW1wYWJsZS9UaW1lc3RhbXBhYmxlQmVoYXZpb3IucGhw) | `95.94% <100.00%> (+0.11%)` | :arrow_up: |

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[wollanup]

Hi @michbeck and @dereuromark ! If you're interested by this PR, could you help me with the tests errors (8.2, pgsql) please ? I'm not sure to find the cause easily. Maybe a problem saving a book [here] ?(https://github.com/propelorm/Propel2/blob/4f36eea97eb5fcf451a4f80430a728be92b70ac8/tests/Propel/Tests/Runtime/ActiveQuery/ExistsTest.php#L254)

Thanks for any help !