Refactor Build System

[kanej]

As part of the Hardhat v3 work we want to make the build system a top level component. Currently it is expressed as a collection of tasks. Our intent is to convert it into a standard component outwith the task subsystem, that will be provide a small number of hook in points that can be leveraged from a compile task.

TODO

• [ ] Move the build tasks into their own folder within core at the top level
• [ ] Mirror that move for the compilation and build based tests
• [ ] Refactor the build system to be standard code rather than tests