Rework run_server endpoint argument to evade issues with colon

[grossjct]

Fixes #445

Changes proposed in this pull request:

• Split the endpoint argument of run_server into 4 arguments for each part
• Avoids the need of a colon in the arguments
• This evades the issue of the colon being the seperator for the method arguments, which makes it not usable in an argument

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[Copilot]

Pull request overview

This PR updates the server benchmark runner configuration to avoid using a colon-containing endpoint argument (which conflicts with olmocr.bench.convert’s colon-delimited method[:key=value...] parsing), by splitting the endpoint into separate components.

Changes:

• Replaces the single endpoint argument with endpoint_scheme, endpoint_hostname, endpoint_port, and endpoint_path.
• Constructs the full endpoint URL from the new components inside run_server.

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