feat(transport/all): Add ability to specify []otelhttp.Opts for transport when create new HTTP client

[surik]

See #3138

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[quartzmo]

@surik Can you please open a feature request issue in this repo explaining your need for otelhttp.Option in the HTTP Client? Thank you.

[surik]

Hi @quartzmo, I've opened a request #3138

[quartzmo]

Kokoro CI failed with staticcheck:

internal/settings.go:193:64: type assertion to the same type: o already has type otelgrpc.Option (S1040)

[codyoss]

For both this and the gRPC package this change is fine to make, but it won't actually enable the feature for most users -- that is because these packages, by default, delegate to our new auth library which has its own transport packages: https://pkg.go.dev/cloud.google.com/go/auth

At the very least I think we should add some TODOs and keep the issue open until this is plumbed all the way through to the new auth packages. See the newClientNewAuth function in this file as an example of how we delegate calls to this new library.

[surik]

Thank you @codyoss! I added a todo.

[codyoss]

We are going to hold off on this PR for now as our team is investigating some cross language support for open telemetry yet this year. For the sake of consistency I don't want to add new options yet. We will make sure to bring up this user journey as we thoughtfully design this integration.