Split packages/core into packages/core and packages/browser

[carterworks]

Warning

This PR is based off of #1414, which itself is based off of #1412, so this should not be merged until they are.

Description

This PR changes the publishing artifact from being the packages/core folder to a new folder called packages/browser. And that folder gets the @adobe/alloy, and then the core folder appropriately gets the name @adobe/alloy-core. The intent is that both of these packages will be published to NPM.

The core package will be buildless, and then all build steps as well as integration and functional tests, anything to do with a browser stays in the browser package.

No functionality or browser specific functionality has been removed from the packages, the core package, but that is kind of the next step, and hopefully that work can be parallelized.

As it stands right now, the CI test and the publishing workflow still need to be completed. But right now this branch is 95% done.

Related Issue

Motivation and Context

Screenshots (if appropriate):

Checklist:

• I have signed the Adobe Open Source CLA or I'm an Adobe employee.
• I have made any necessary test changes and all tests pass.
• I have run the Sandbox successfully.

[carterworks]

Serban has identified some issues

• Make custom build script default to outputting in the current directory, not the project root
• There are a few package-level npm scripts that just run the root-level script, like for testing. This could lead to recursive script issues. If running tests for multiple packages at the same time, we should fix that.
• Unit tests have been a little flakey
• The typescript language server complains, when in the browser package, that there are no type definitions for the core package. We should create a base level TypeScript config at the top level and then each package should also have a TypeScript config, or even better jsconfig.json, and then use that package or that base level TypeScript config in each of the packages.
• Be consistent in how .browserslist is used/defined/applied