Fix wrong origin returned by cagg_get_bucket_function_info

[fabriziomello]

In #7042 we refactored the code for getting the time bucket function info to read information from the stored query tree on Postgres metadata.

But when an origin was not specified it was returning a wrong value instead of NULL. Fixed it by properly dealing with non-defined origin and also simplified a bit the code to process time bucket parameters.

Disable-check: force-changelog-file

[codecov]

Codecov Report

Attention: Patch coverage is 88.23529% with 2 lines in your changes missing coverage. Please review.

Project coverage is 81.24%. Comparing base (59f50f2) to head (1b66597).
Report is 652 commits behind head on main.

Files with missing lines	Patch %	Lines
tsl/src/continuous_aggs/common.c	88.23%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7533      +/-   ##
==========================================
+ Coverage   80.06%   81.24%   +1.17%     
==========================================
  Files         190      230      +40     
  Lines       37181    43034    +5853     
  Branches     9450    10764    +1314     
==========================================
+ Hits        29770    34964    +5194     
- Misses       2997     3713     +716     
+ Partials     4414     4357      -57     

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[antekresic]

Looks good in general, left a question about readability and setting the right expectations in the code.

[antekresic]

Why not make it explicit that there can only be 3 or 5 arguments? I'd move this into a single check expecting exactly 5 arguments since 4 arguments should not happen.

[fabriziomello]

But FuncExpr arguments is not aligned with the actual function signature, for example this function call: time_bucket('1 hour', ts, timezone=>'America/Sao_Paulo', offset=>'1 day') is actually the 5 arguments time bucket but FuncExpr has 4 arguments (FuncExpr->args). The logic to decide what to do with arguments is on process_additional_timebucket_parameter.