### Does this PR have any customer impact?
No.
### Type (Feature, Refactoring, Bugfix, DevOps, Testing, Perf, etc)
Feature.
### Does it involve schema level changes? (Table, Column, Index, UDF, etc level changes)
No.
### Are you introducing any new config? If yes, do you have tests with and without them being set?
Yes.
### ChangeLog (Refer [Template](../oss/CHANGELOG.md))
### Description
Add OSS background_worker initial jobs framework. For this initial version, only schedulable jobs are allowed (i.e. jobs that run on timed intervals). The background worker loop has a latch timeout with a predefined duration of 10 seconds that is configured through a GUC. Every time this timeout occurs, it iterates on the JobRegistry array.
1. Checks if the job is running and if it timed out (i.e. running longer than timeoutInSeconds). If yes, cancels the query and finishes libpq connection.
2. Checks if the job finished running (i.e. libpq connection isn't busy). If yes, finishes the libpq connection.
3. Runs the job if its scheduled interval has reached (i.e. currentTime - lastStartTime >= scheduledInterval). Each job execution has its own libpq connection to the database.
In order to add a new job callers must pass a BackgroundWorkerJob structure to RegisterBackgroundWorkerJob.
----
#### AI description (iteration 1)
#### PR Classification
This pull request introduces a new feature by adding an OSS background worker jobs framework.
#### PR Summary
The changes implement a framework for scheduling, executing, and managing background jobs within the background worker process. This provides structured job processing with timeout, cancellation, and configuration support.
- **`src/background_worker/background_worker.c`**: Added job management functions (e.g., ManageJobs, ExecuteJob, CanExecuteJob, CheckJobCompletion, CancelJobIfTimeIsUp, ValidateJob) and integrated job scheduling in the main loop.
- **`include/background_worker/background_worker_job.h`**: Introduced new structures for defining background worker jobs and their execution objects.
- **`src/api_hook_impl.c`**: Added a hook function to retrieve background worker jobs for registration.
- **`src/configs/background_job_configs.c`**: Defined new configuration variables (GUCs) to enable background worker jobs.
- **API Hooks and Connection Management Files**: Updated declarations and functions (e.g., in `include/api_hooks_def.h` and connection management files) to support connection handling necessary for job execution.
<!-- GitOpsUserAgent=GitOps.Apps.Server.pullrequestcopilot -->
Related work items: #4225917
### Does this PR have any customer impact?
No
### Type (Feature, Refactoring, Bugfix, DevOps, Testing, Perf, etc)
Refactoring
### Does it involve schema level changes? (Table, Column, Index, UDF, etc level changes)
No
### Are you introducing any new config? If yes, do you have tests with and without them being set?
No
### Release Note (Refer [Template](../docs/release_notes/pgmongo_template.md))
### Description
Migrate tests to documentdb and clean helio references from source
----
#### AI description (iteration 1)
#### PR Classification
Code cleanup and migration of tests.
#### PR Summary
This pull request migrates tests from `helio` to `documentdb` and removes all references to `helio` from the source code.
- `oss/pg_documentdb/src/test/regress/expected/commands_update.out`: Replaced all `helio` references with `documentdb` and updated test cases accordingly.
### Does this PR have any customer impact?
No
### Type (Feature, Refactoring, Bugfix, DevOps, Testing, Perf, etc)
Refactoring
### Does it involve schema level changes? (Table, Column, Index, UDF, etc level changes)
No
### Are you introducing any new config? If yes, do you have tests with and without them being set?
No
### Release Note (Refer [Template](../docs/release_notes/pgmongo_template.md))
### Description
Remove helio references from documentdb
Remove helio references from documentdb_distributed
----
#### AI description (iteration 1)
#### PR Classification
Code cleanup
#### PR Summary
This pull request removes references to "helio" and replaces them with "documentdb" in the sources of `documentdb` and `documentdb_distributed`.
- `metadata_cache.h` and `metadata_cache.c`: Replaced "Helio" with "DocumentDB" in variable names and function names.
- `pgmongo.c`: Updated include statements and function calls to use "documentdb" instead of "helio".
- `planner.c`: Updated planner function and related calls to use "DocumentDBApiPlanner".
- Moved several header files from `helio_*` to `documentdb_*` naming convention without code changes.
- `commands_common.c` and `create_indexes.c`: Updated function calls and variable names to use "DocumentDB" instead of "Helio".
Lucas Borges Fernandes
Zinan Ren