[CDF-25252] 😋 SearchConfigYAML (#1756)

# Description

**Context** In Toolkit, we implement pydantic for all DTO (data transfer
objects) in the API. This is instead of using the DTO classes from the
`cognite-sdk`. We do this for two reasons. The Toolkit DTO objects
deviates from the API in some small ways, for example, we do not have
internal IDs, instead we use external ID such that a resource can be
deployed across multiple CDF projects. In addition, `pydantic` classes
gives much better feedback to the user if they are not following the
syntax of the YAMl.

This PR implements the `SearchConfigYAML` for the search config API.

**Note** I found (or Gemini) a bug/confusing error in
`validate_resource_yaml_pydantic` when running tests for
`SearchConfigYAMl`. Fixed it and updated

## Changelog

- [x] Patch
- [ ] Minor
- [ ] Skip

## cdf

### Improved

- Improved location information for `ResourceFormatWarning`s.

## templates

No changes.
