feat: HTTP pull source

[edlee2121]

Is your feature request related to a problem? Please describe.
Desirable to have a source that periodically pulls from an http endpoint to generate messages.
This would be very useful for demos as well since we can pull from services that everyone can access rather than just synthetically generated data.

Describe the solution you'd like
A source that generates a stream of data by periodically pulling from an http endpoint.

Describe alternatives you've considered
Using an S3 bucket as a source (not many interesting data is available to everyone in S3 buckets).

Additional context
None

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Message from the maintainers:

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[vigith]

We might be able to do this using our current generator source with a UDF that can do cURL.