WIP use dprint for internal code formatting

[ry]

I'm not sure we're ready for this, but I wanted to put up my half attempt to get this working.

Problems:

• configuration for "deno fmt" and "dprint" is now split between cli/fmt.rs and tools/dprint_config.json
• still need prettier for json and md
• need to update CI to install dprint binary
• not all configurations supported via JSON (?)

[trivikr]

As per comment #4507 (comment), two changes pending in dprint related to deno migration https://github.com/dsherret/dprint/milestone/2

[dsherret]

There was a bug related to this config option that is now fixed: https://github.com/dsherret/dprint/issues/180

[dsherret]

You can replace this with...

{
    "deno": true
}

...to have the same config (I renamed this from "prettier" to "deno" because it was different on trailing commas).

Then you may want to test out and provide feedback on the new preferSingleLine option:

{
    "deno": true,
    "preferSingleLine": true
}

...I'm still working on improving that, but I'll turn it on soon in the deno config because it's what prettier does.

Main things for me still are:

1. More preferSingleLine config.
2. Improve binary expression formatting (ex. 1 + 2)

[bartlomieju]

Still waiting on dprint/dprint#81. This PR got stale; closing without merge.