Expose a "glean" command

[Dexterp37]

This exposes a "glean" command to be used as an interface for running the glean_parser by glean.js
consuming products. It takes care of setting up a virtual environment and making sure that the parser
and its dependencies are up to date.

How to test this:

• Add glean.js to a project via npm link
• Run npx glean .... and check the generated output.

For rally, I had this output:

dexter@DX-WORKHORSE:/mnt/d/Mozilla/rally/core-addon$ npx glean translate metrics.yaml pings.yaml -f javascript -o public/generated
Checking for a Glean virtual environment at /mnt/d/Mozilla/rally/core-addon/.venv
Using Glean virtual environment at /mnt/d/Mozilla/rally/core-addon/.venv

TODO:

• Test on MacOS.
• Verify that the command gets published.
• Add unit tests? (we're not going to add them, but instead we're adding this command to the samples)

[brizental]

Tested on MacOS and it works. Let's file a follow up for showing some status, specially the first run takes a long long time and it looks like it's frozen. Can you send commits with changes to the sample extensions? Currently they rely on a globally installed glean_parser.

[Dexterp37]

Tested on MacOS and it works. Let's file a follow up for showing some status, specially the first run takes a long long time and it looks like it's frozen. Can you send commits with changes to the sample extensions? Currently they rely on a globally installed glean_parser.

I filed https://bugzilla.mozilla.org/show_bug.cgi?id=1699391 and https://bugzilla.mozilla.org/show_bug.cgi?id=1699392 as potential follow-up work.

[brizental]

r+wc. This is great.