fix(errors) use new header tables in error handler (#5673)
fix(errors) use new header tables in error handler (#5673)

Create new header tables for each run of the error handler. Previously,
HEADERS_JSON and similar were defined at the module level, and the error
handler used the same table each time, passing it by reference to
kong.response.exit().

The exit-transformer plugin allows kong.response.exit() to modify these
tables, resulting in an issue where its modifications would persist for
subsequent requests, even if the exit-transformer did not apply to them.
Creating new tables for each run of the error handler avoids this.
Kong/kong,Kong/kong,Kong/kong