[cql2-text] NOT operator is not supported

Initially raised in https://github.com/stac-utils/stac-fastapi/issues/473, it appears as though the `NOT` operator is under- or un-supported for CQL2-TEXT. E.g.

```text
collection NOT LIKE 'not-a-collection-id'
```

https://github.com/geopython/pygeofilter/issues/22 appears to be a similar issue that asks about general CQL2-TEXT support, but I thought a specific issue for this problem might be helpful. Please feel free to close if you feel as though this is a duplicate of #22 (or another issue). Thanks!

Start by reviewing the CQL2-TEXT parsing behavior for the example `collection NOT LIKE 'not-a-collection-id'`, then compare the related discussion in stac-utils/stac-fastapi#473 and geopython/pygeofilter#22. Done means the NOT operator is supported for this expression and its behavior is covered by an appropriate test.

Written by the indexing model from the issue text.