implement the azle dfx extension and update all example projects

[lastmjs]

Closes #1029
Closes #1124

This implements the initial Azle extension! All examples with working tests have been updated to use the extension. Documentation is out-of-scope and will be done in a later PR, there's like one little documentation change in here.

Some questions to be answered with design discussions during review:

• Should we keep the npx azle install-dfx-extension command? Is there some more appropriate way to install the extension? (The decision is this: we will keep the manual installation for now, because dfx start does not work inside of a directory with a dfx.json file with an extension that hasn't been installed. This means that the extension must be installed before the user runs dfx start. I'm not sure if there's a good automatic way to do this right now)
• What do we do about naming clashes between dfx and Azle in the dfx.json? (We should probably nest azle-specific commands, let's wait on dfinity providing a nice nesting structure? We could always move forward on this now though, which might be a good idea because we're introducing breaking changes now anyway)
• When should we release this? Should we merge this now? It's going to take a few weeks before this comes out in a dfx release with a hard number, but we could use the release that we're using for testing