Route registration and exception improvements

Upgrading

composer require laravel-json-api/laravel --no-update
composer up "laravel-json-api/*"

Exceptions converted to JSON:API errors when debug mode is on now include all previous exceptions.

Registering routes no longer results in the server instance being thread-cached. This more accurately reflects
production environments, where routes would be cached so there would be no thread-cached JSON:API server when handling
a HTTP request. This means tests (and development environments where routes are not cached) more accurately behave in
the same way as production environments.
Exceptions thrown during the encoding process are no longer caught and re-thrown as previous exceptions. This is due
to the number of questions we receive from developers who do not check previous exceptions, despite exception messages
stating that there is a previous exception to look at.