otelhttp: Deprecate `WithPublicEndpoint` in favor of `WithPublicEndpointFn`

[dmathieu]

[n2p5]

Hi! I'm looking to make my first contribution to this repo and this issue caught my eye. I noticed that WithPublicEndpoint and WithPublicEndpointFn exist in:

otelhttp
otelgrpc
otelmux
otelrestful

Based on the name of this issue we're only interested in Deprecating otelhttp, but would it make sense to address this across these other areas as well?

[flc1125]

Based on the name of this issue we're only interested in Deprecating otelhttp, but would it make sense to address this across these other areas as well?

I think we can first resolve the issue with otelhttp, which can serve as a stability reference standard for other components in the future.

[flc1125]

@n2p5 Assigned to you