Change config v3 format for query_collections. Make possible to store it in directory format

### Is your proposal related to a problem?

We have much more queries in AllowList then registered DB objects.

It seems illogical to work with db objects in separate files but query collection is "all-in-one".

It would be more convinient to have abiltiy to work with them as with collection of files.

### Describe the solution you'd like

I would like to have ability instead of single file `query_collections.yaml` to have a directory `query_collections.yaml.d`.

E.g.
```bash
metadata/query_collections.d
├── mutation-ADD_MEASURE_TIME.yaml
├── mutation-ADIT_CREATE_DECLARATION_MESSAGE.yaml
├── query-ADIT_GET_DECLARATION_ACTION_DATA.yaml
...
```

### Describe alternatives you've considered

### If the feature is approved, would you be willing to submit a PR?

I would like to do that. Although I don't know hasura cli sources yet.