Investigate allowing different templating per detector vs per run for the start document path provider

[abbiemery]

There is a desire to allow different detectors within a run to have differently structured file names. Currently the start document path provider allows for a custom template to be provided, but it applies the same across all detectors in a run. We should investigate how we could differentiate between detectors for this templating

Acceptance Criteria

• Know if this is possible within blueapi
• If there are few options, have the implementations drafted out so a discussion can be had about the desired direction

[callumforrester]

So currently we are allowing people to insert "template": "blah-blah-{detector}" into the start document, could instead have

"template": {
    "default": "blah-blah-{detector}",
    "my-special-detector": "{detector}-blah-blah"
}

[abbiemery]

There is a proof-of-concept PR in numtracker to support this but as the detector templating in numtracker is not used yet, this can be deferred for now.

DiamondLightSource/numtracker#103