[ENH] Use figment configuration for chroma-load

[rescrv]

This mirrors the compactor and query services (and can even merge with
their configs if we so choose).

[github-actions]

Reviewer Checklist

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Testing, Bugs, Errors, Logs, Documentation

• Can you think of any use case in which the code does not behave as intended? Have they been tested?
• Can you think of any inputs or external events that could break the code? Is user input validated and safe? Have they been tested?
• If appropriate, are there adequate property based tests?
• If appropriate, are there adequate unit tests?
• Should any logging, debugging, tracing information be added or removed?
• Are error messages user-friendly?
• Have all documentation changes needed been made?
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System Compatibility

• Are there any potential impacts on other parts of the system or backward compatibility?
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Quality

• Is this code of a unexpectedly high quality (Readability, Modularity, Intuitiveness)

[eculver]

This may be a silly question, but is it common for the type to indicate what it's doing (aka a verb) versus being just a noun? Speicifically, what I'm wondering if ServiceConfig is appropriate here vs LoadServiceConfig? Just curious.

[rescrv]

"Load Service" is a proper noun in this context.

[Sicheng-Pan]

Lgtm