Import _ERROR constants into global debug space
Summary:
Keruald sites use GENERAL_ERROR, HACK_ERROR, and SQL_ERROR
to categorize fatal error messages.
One of our current goals is to help sites to eliminate the includes/ directory,
allowing them to refer to Keruald libraries for generic code or to their own
engine classes for domain-specific code.
As such, importing the constants enables the use of the legacy message_die
function, either directly in the global space or migrated to an error handler
class.
Ref T2145
Test Plan: Tested with Obsidian Workspaces code.
Reviewers: dereckson
Reviewed By: dereckson
Maniphest Tasks: T2145
Differential Revision: https://devcentral.nasqueron.org/D3787