[Feature Request] Accept float and int metrics

[bergundy]

Since our goal with metrics is to expose a generic interface for metrics recording in our lang SDKs using industry standards, we should expand the metrics API in core to accept floats and not just ints.

https://github.com/temporalio/sdk-python/pull/384#discussion_r1321823495

[cretz]

Since our goal with metrics is to expose a generic interface for metrics recording in our lang SDKs using industry standards

I am not sure this is a goal. I think it's "expose the same interface core needs". Same in the Go SDK. There are OTel metric types we're not exposing (e.g. up/down counter). Having said that, I don't see why float shouldn't be added.