Make it easier to test VRL transformations + schema changes

[Samrose-Ahmed]

Overview

It is currently difficult to test VRL and schema changes in Matano. It requires a deployment and results in errors that make it hard to ascertain the issue.

Goal

Add functionality to be able to test changes to VRL transformations and schema's easily while developing.

[cscetbon]

@Samrose-Ahmed have you tried to write a simple example ? I've been trying to do something like this but I get

the trait bound `vrl::prelude::ArgumentList: From<HashMap<&str, vrl::value::Value>>` 
is not satisfied required for `HashMap<&str, vrl::value::Value>` to implement
 `Into<vrl::prelude::ArgumentList>`

when I copy an existing test for a new function I added