WG-prioritization: retrieve all T-compiler WG meetings

[apiraino]

For WG-prioritization agenda, add all Rust compiler WG meetings happening in the following week.

This new bit of the agenda is added automatically by calling the google calendar API, needs the caller to set a new env var (GOOGLE_API_KEY) with the API token.

Was mentioned in a past T-compiler meeting, I've attempted an implementation.

r? @spastorino

[spastorino]

@apiraino in general looks good to me.

[apiraino]

@spastorino thanks for the comments. I've pushed all your suggestions. I think the test failure is just a warning from unrelated code changes (which I will address in a separate pr)

[apiraino]

@spastorino ok, rebased into a single commit