Add literal APIs for PrecisionTimestamps

[scgkiran]

Only last commit needs to be reviewed. Other changes are part of PR #43

[codecov]

Codecov Report

Attention: Patch coverage is 93.69369% with 14 lines in your changes missing coverage. Please review.

Project coverage is 53.40%. Comparing base (e77df67) to head (aafa57b).
Report is 1 commits behind head on main.

Files	Patch %	Lines
expr/literals.go	80.95%	4 Missing ⚠️
literal/decimal_util.go	90.24%	2 Missing and 2 partials ⚠️
literal/utils.go	96.52%	3 Missing and 1 partial ⚠️
types/precison_timestamp_types.go	95.55%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #47      +/-   ##
==========================================
+ Coverage   52.31%   53.40%   +1.08%     
==========================================
  Files          21       23       +2     
  Lines        6013     6179     +166     
==========================================
+ Hits         3146     3300     +154     
- Misses       2678     2687       +9     
- Partials      189      192       +3     

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[jacques-n]

This is still marked as draft. Should this be marked ready for review?

[jacques-n]

It looks like this has a merge conflict. I probably won't be able to review and tomorrow but it would be good if you fixed that so if it is good to go, I can merge it. Thanks

[scgkiran]

It looks like this has a merge conflict. I probably won't be able to review and tomorrow but it would be good if you fixed that so if it is good to go, I can merge it. Thanks

Done