feat!: refactor into monorepo with compile and cli packages

[chrispcampbell]

Fixes #191

This is an initial round of refactoring that converts the existing sdeverywhere package into separate @sdeverywhere/compile and @sdeverywhere/cli packages. This sets the stage for adding more packages (build, runtime, check, etc) in the coming days.

For this PR, I've kept the implementation as untouched as possible. The changes are limited to:

1. moving sde command-related files to the cli package
2. moving core compiler (preprocess, parse, generate) files to the compile package
3. updating imports and moving some functions/dependencies to one side or the other so that there is a clean split
4. removing some repeated boilerplate (e.g., parser creation) and replacing with shared functions

The only notable exception is that I've removed the sde generate --genhtml command and supporting web files. There will be a replacement for this implemented using the plugin API; this avoids having it baked into the core, so that we can make it more configurable and have fewer dependencies in core.

With these changes in place, we now have a pretty minimal API surface for the compile package. The exact API is subject to change before 1.0, but at least now the compile package is well isolated:

export { generateCode } from './CodeGen.js'
export { parseAndGenerate, printNames } from './Entry.js'
export { canonicalName } from './Helpers.js'
export { parseModel } from './Parser.js'
export { preprocessModel } from './Preprocessor.js'
export { readDat } from './ReadDat.js'

For the commit message (and the changelog):

BREAKING CHANGE: The sdeverywhere package is deprecated and effectively replaced by @sdeverywhere/cli. Additionally, the sde generate --genhtml command and supporting code has been removed and will be replaced with a different solution in the near future.

/cc @ToddFincannon