[fix](Nereids): fix bugs about date function

[keanji-x]

Proposed changes

1. Add unixtime type to represent unix-timestamp. It's -1 when the real arguments > INT.MAX. We don't use int because the long value will be cast to INT.MAX and then we always get the largest time 2038-1-19 rather than null
2. Change the scale of default datev2 from 0 to 6 so we can be compatible the smaller precision

Problem summary

Describe your changes.

Checklist(Required)

1. Does it affect the original behavior:
   • Yes
   • No
   • I don't know
2. Has unit tests been added:
   • Yes
   • No
   • No Need
3. Has document been added or modified:
   • Yes
   • No
   • No Need
4. Does it need to update dependencies:
   • Yes
   • No
5. Are there any changes that cannot be rolled back:
   • Yes (If Yes, please explain WHY)
   • No

Further comments

If this is a relatively large or complex change, kick off the discussion at dev@doris.apache.org by explaining why you chose the solution you did and what alternatives you considered, etc...

[hello-stephen]

TeamCity pipeline, clickbench performance test result:
the sum of best hot time: 34.43 seconds
load time: 502 seconds
storage size: 17122409472 Bytes
https://doris-community-test-1308700295.cos.ap-hongkong.myqcloud.com/tmp/20230119162344_clickbench_pr_84284.html