Move AST to standalone tiny package

[blitz-1306]

Current package has two goals:

• Handle compile routines of Solidity sources. This requires package to rely on Solc compiler, do file system lookups, allow compiler guessing and downloading.
• Handle AST processing. This requires to handle historically various types of Solidity AST (produced by compiler), tree travesal, AST-to-source writing, making new AST nodes, also parse types to a type tree.

We are considering to move AST processing to a standalone tiny package in near future. Current reasoning:

• Compile-related functionality forces to load ~20 megabytes by always shipping and loading latest WASM compiler.
• Compile-related functionality requires to do a file system lookups. This is useful when using sol-ast-compile or developing side CLI packages, but not that suitable in case if someone would like to use typed AST in browser.
• AST processing actually does not force to use our compiling routines. In other words, ASTReader does not care how source were compiled - it requires only compiler output. Users may use native, wasm or whatever compiler to compile source and just supply returned data.

A plan:

• Move AST-related functionality to a side package and publish it to NPM.
• Clean up this package from AST logic.
• Add AST package as dependency to maintain BC of this package however possible.

We are publising this to receive opinions and infrom about further changes. Thanks for your time and attention.

[blitz-1306]

Current set of considerations:

• [ ] both: update README in both repositories.
• [ ] both: publish to NPM as two separate packages.
• [ ] both: release cycle would be longer, need to update/release ast and compile packages and have common flow for release procedure.
• [ ] both: need to figure out what to do with the docs.
• [ ] ast: #117.
• [ ] ast: should not have a docker image.
• [ ] ast: would miss integration tests, so there would be necessary to figure something (maybe use WASM-produced and native-produced artifacts).
• [ ] compile: should use ast as dependency.
• [ ] compile: should contain compile-related logic and executable (sol-ast compile)
• [ ] compile: should have integration tests.
• [ ] compile: ammouncement in README that packages are now separated.
• [ ] compile: probably reexport ast to maintain backward compatibility.

[blitz-1306]

@cd1m0 Hello. Consider some of the steps above if there would be some spare time. Thanks.

[cd1m0]

These are all valid considerations. I just want to comment on two of them:

1. "release cycle would be longer": you are right, this is a downside of this approach. I don't know of a way to avoid this

2. "ast would miss integration tests": yeah, this will be a problem. One thing we could try is to add the compilers and file-system packages as dev dependencies, and copy over a minimal set of logic for compiling contracts. Then we might still be able to adapt some of the integration tests from the compile repo?

Everything else in the considerations seems ok to me.