Generate `httpMalformedRequestTests` (#1213)

Smithy defines one trait specifically for the behavior of server
protocol implementations.

From https://awslabs.github.io/smithy/1.0/spec/http-protocol-compliance-tests.html#httpmalformedrequesttests:

> The `httpMalformedRequestTests` trait is used to define how a malformed
> HTTP request is rejected given a specific protocol and HTTP message.
> Protocol implementations MUST assert that requests are rejected during
> request processing.

This commit implements code generation for these tests. The ones for the
restJson1 protocol have been added to the list of failing tests. These
should begin passing once we start implementing constraint traits
https://awslabs.github.io/smithy/1.0/spec/core/constraint-traits.html