STAC: Add Support for `ids`, `collections` query parameters in STAC search endpoint

**Is your feature request related to a problem? Please describe.**

Currently the STAC Search API supports `bbox`, `datetime`, `limit`, and `offset` query parameters:

https://github.com/geopython/pygeoapi/blob/533eb0a52fb90b8513ed460ce787f1e41912e280/pygeoapi/api/stac.py#L342-L347

To add capabilities of [STAC Simple Search](https://api.stacspec.org/v1.0.0/item-search/#tag/Item-Search/operation/getItemSearch), we need to add support for `ids` and `collections` parameters. `intersects` is optional in the spec, and since we already support `bbox`, that can be deferred for now.

**Describe the solution you'd like**

Support of `ids` and `collections` filters.

**Describe alternatives you've considered**

This could potentially be filtered on the client side, but that is not ideal.

**Additional context**

N/A