Modify the github build so that it builds from first principles

[Claude-at-Instaclustr]

The only real source files for this project are

1. grammar.js
2. test/corpus/*

There is a demo program

1. src/main.rs

Everything else comes from either the tree-sitter build package or cassandra example blogs or other documentation concerning the CQL structure -- some of which are wrong.

The package should be reduced to be just the grammar and test corpus for packaging and the main.rs fixed up as a test/development tool.

All other components should be removed and

1. The github build script execute an install of the tree-sitter main line code and then build the package from the grammer, including the tests.
2. The readme should be updated to explain how to setup the environment for the developer.