Cache calls to promisify present in hot paths

[alcuadrado]

This PR implements two performance optimizations. See #598 for more info.

[lgtm-com]

This pull request introduces 1 alert when merging 35b4b6c into 195bba7 - view on LGTM.com

new alerts:

• 1 for Unused variable, import, function or class

[s1na]

Looks good. Thanks for digging deep and fixing this so quickly Patricio!

[holgerd77]

Just another 2 cents comment after merge: it would have been nice if there would be some comments on these changes in the code so that it gets more transparent for others what is actually happening here and why these changes have been introduced, otherwise there is the risk that this gets lost again.

Another thing, logically unrelated by topically related: it would of course be fabulous to have benchmarking in CI, also with a threshold to reject the build. Does something like this actually exist?

[alcuadrado]

Just another 2 cents comment after merge: it would have been nice if there would be some comments on these changes in the code so that it gets more transparent for others what is actually happening here and why these changes have been introduced, otherwise there is the risk that this gets lost again.

Oh, this is a great idea! Will make a small PR with this.

Another thing, logically unrelated by topically related: it would of course be fabulous to have benchmarking in CI, also with a threshold to reject the build. Does something like this actually exist?

I'm not sure. Running performance tests on every push may be super slow.

I sometimes follow TypeScript issues, and they have a bot that runs them on demand. That could be nice.