Get rid of Candid files if possible, put them in the .azle directory along with the other generated files

[lastmjs]

It seems best to take care of dfx extensions first, as it will be less of a burden on everyone: #1124

Candid and its generated files are possibly confusing to new developers, and I believe are generally an unnecessary extra concept especially when dealing with HTTP canisters.

Let's remove candid files from the developer's project by default for HTTP canisters...we'll put them in .azle somewhere. Let's consider if we should do this for all canisters by default, and maybe only put it in their directory if they specify the candid property differently in their dfx.json.

In fact, maybe dfx extensions is a prerequisite to this. I will think about that.