feat(internal): Miscellaneous improvements

[gibson042]

Description

• Add defineName utility for naming otherwise anonymous functions.
• Improve typing.
• Promote errors.js into an @endo/errors polyfill (removing this dependency will allow pure-JS utilities to use Fail and q).

Security Considerations

Using the Fail polyfill without SES (or importing it before SES) will produce errors with censorship-free messages. This is expected only for scenarios in which SES is not loaded at all, but if we are concerned, then it could incorporate a time-of-use check that e.g. globalThis.Fail and/or globalThis.assert?.Fail are undefined (or that globalThis.lockdown is, or whatever we deem to be the best predicate for detecting SES).

Scaling Considerations

n/a

Documentation Considerations

No new concerns, although we could definitely do a better job of documented what's in package "internal" and how to use it.

Testing Considerations

These are likewise lacking. I suppose a lot could be cribbed from Endo.

Upgrade Considerations

n/a