refactor: consolidated registry into a class, made registry hierarchical

[pavelgj]

No description provided.

[pavelgj]

Ping

[mbleigh]

What about withRegistry(), withTempRegistry()? I'm not sure withIsolatedRegistry has a lot of utility

[mbleigh]

Also should withTempRegistry perhaps have a way to be used without being a wrapper function? So you could do something like:

before(() => {
  enableTempRegistry();
});

after(() => {
  cleanupTempRegistry();
});

// then all your tests

[pavelgj]

Also should withTempRegistry perhaps have a way to be used without being a wrapper function? So you could do something like:

before(() => {
  enableTempRegistry();
});

after(() => {
  cleanupTempRegistry();
});

// then all your tests

Simplified this PR, it's just about consolidating registry into a class -- single global state (registry object)