Don't export OpenLoco / OpenGraphics objects with scenario or save files

[shusaura85]

Description of changes

Adds isOpenLoco() function to Object.h mirroring isCustom() and isVanilla functions and expanded the check when exporting plug-in objects to also check isOpenLoco() before saving objects.
Also updates Object Selection window replacing the raw comparison with the new function for the object source filtering options.

Rationale behind changes

This affects what objects are saved in scenario or save files. Objects marked as OpenLoco (such as OpenGraphics objects) should not be included in saved scenarios or save games (when "export plug-in objects with save games" is enabled).
OpenGraphics are part of every OpenLoco install so there's no point in including them with each save increasing the file size (using "North America Expanded" region included in v26.09 (with no other changes to other scenario creation options) would create a scenario file of around 15MB compared to around 0.8MB if OG objects not included)

Suggested testing steps

1. Make sure "export plug-in objects with save games" is enabled in options.
2. Create a new scenario with v26.09 using "North America Expanded" region to use OG objects and save.
3. Check scenario file size
4. Repeat steps 2 and 3 with the artifact build for this PR
5. Compare file sizes (or check saved objects in files using object editor)

Did you use AI to help find, test, or implement this issue or feature?

No AI was used for these changes.