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 82.19%. Comparing base (59f50f2) to head (172bc86).
Report is 655 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%   82.19%   +2.12%     
==========================================
  Files         190      230      +40     
  Lines       37181    43280    +6099     
  Branches     9450    10882    +1432     
==========================================
+ Hits        29770    35574    +5804     
- Misses       2997     3390     +393     
+ Partials     4414     4316      -98     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[antekresic]

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

[mkindahl]

There is some old odd choices regarding the time_bucket function implementation, but the changes here are good.

[timescale-automation]

Automated backport to 2.17.x not done: cherry-pick failed.

Git status

HEAD detached at origin/2.17.x
You are currently cherry-picking commit 9e4016799.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   tsl/test/expected/cagg_migrate_function-14.out
	modified:   tsl/test/expected/cagg_migrate_function-15.out
	modified:   tsl/test/expected/cagg_migrate_function-16.out
	modified:   tsl/test/expected/cagg_migrate_function-17.out
	modified:   tsl/test/expected/cagg_query.out
	modified:   tsl/test/expected/cagg_query_using_merge.out
	modified:   tsl/test/expected/cagg_utils.out

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	both modified:   tsl/src/continuous_aggs/common.c
	deleted by us:   tsl/test/expected/cagg_query-15.out
	deleted by us:   tsl/test/expected/cagg_query-16.out
	deleted by us:   tsl/test/expected/cagg_query-17.out
	deleted by us:   tsl/test/expected/cagg_query_using_merge-16.out
	deleted by us:   tsl/test/expected/cagg_query_using_merge-17.out
	both modified:   tsl/test/sql/CMakeLists.txt

Job log