Initialize error data using constructors directly

[bjfish]

This avoids using the Kernel#raise string message parameter to initialize custom data for errors in favor of initializing with the data directly as described here:
#2164 (comment)

This is also consistent with other usages like:

grape/lib/grape/middleware/versioner.rb

Line 29 in e0f412c

raise Grape::Exceptions::InvalidVersionerOption.new(strategy)

grape/lib/grape/endpoint.rb

Line 129 in e0f412c

raise Grape::Exceptions::MissingOption.new(key) unless options.key?(key)

[grape-bot]

	2 Warnings
⚠️	There're library changes, but not tests. That's OK as long as you're refactoring existing code.
⚠️	Unless you're refactoring existing code or improving documentation, please update CHANGELOG.md.

Here's an example of a CHANGELOG.md entry:

* [#2165](https://github.com/ruby-grape/grape/pull/2165): Initialize error data using constructors directly - [@bjfish](https://github.com/bjfish).

Generated by 🚫 Danger

[dblock]

Anything changes for users that may be relying on this that deserves a CHANGELOG/README/UPGRADING?

[eregon]

This look good to me. It should work exactly the same or better, no user visible changes (except maybe slightly faster to build those exceptions).