Improve query template building experience

[ohltyler]

Currently, the only way to override a query in search request processors is via query_template field nested under advanced settings. There is no further help, such as presets, the placeholders and what they mean, etc.

Ideally, we have a more tailored experience, similar to prompt building, which can have presets, present the available parameters that could be injected, and provide more helper text in general regarding why it exists: