[ddtelemetry] Prefix ffi functions with ddog_telemetry

[paullegranddc]

What does this PR do?

• Rename ddtelemetry ffi functions from ddog_handle_* to ddog_telemetr_handle_* and ddog_builder_* to ddog_telemetry_builder_*

Motivation

What inspired you to submit this pull request?

Additional Notes

Anything else we should know when reviewing?

How to test the change?

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For Reviewers

• If this PR touches code that signs or publishes builds or packages, or handles credentials of any kind, I've requested a review from @DataDog/security-design-and-guidance.
• This PR doesn't touch any of that.

[ivoanjo]

Not sure if you want to take the opportunity here to tweak, but for profiling stuff, we usually use a slightly different naming where we use struct names with camel case, e.g. (ddog_Vec_Tag or ddog_prof_Endpoint.

[paullegranddc]

@ivoanjo
Right now, this PR is more about removing confusion and potential collisions on the telemetry ffi, since I just need the right part of my brain convince the left one to make that happen.

If we want to standardise function and type names for all of libdatadog, we probably should write a small rfc now that we have a directory for that, and share it with the profiling and data-pipelines team?

[ivoanjo]

We actually did discuss such standardization shortly before 1.0, see #73 and https://docs.google.com/spreadsheets/d/1iuuSCJ0NcSOpo2RVvkQ8f8ugz2XlEbbpFZLVOg6WioE/edit#gid=0 .