runtime: update runtime to nodejs@16

[chenrui333]

Node 12 has an end of life on April 30, 2022.

This PR updates the default runtime to node16, rather then node12.

This is supported on all Actions Runners v2.285.0 or later.

[chenrui333]

@mishas thanks for merging this, there should be new major release after this PR merge. Thanks! :)

[mishas]

@chenrui333 , I know, but I'm waiting for dependabot to finish doing its thing before releasing.
Thanks for the contribution!

[mishas]

@chenrui333 , I'd like to run something by you:
I did all the work to update to v2.0, but now that I think of it - I'm not sure I should.
Bazelisk is now part of the basic image of the Github actions (since this merge: actions/runner-images#490). I would guess that we should encourage people not to use this action, but use the builtin bazelisk. We indeed do that in the readme of this action.
In such case - it's ok to leave this repo to be used by older action runners - but in that case, they won't be able to use the v2 anyways, would they?

WDYT?

[chenrui333]

I can play two hats of this, I think the setup-* action do has its own use case in case the virtual-environments. Generally speaking, I like setup-* action better than virtual-environment provided one, better visibility and control.