Download updated plugin schemas for v3.4.x

[fabianrbz]

Now that the descriptions were merged into the schemas, we can pull them using the API.

Note:
I've used the kong/kong-gateway-dev latest docker image.
One thing to point out is that I've tried to validate the examples, and one of them is failing:

---------------------------------
| Plugin: application-registration
| Source: ./examples/application-registration/_3.4.x.yaml
| Response Code: 400
| Valid?: ❌
| name: schema violation
| fields: {"service"=>{"id"=>"missing primary key"}}
| code: 2
| message: schema violation (service.id: missing primary key)
---------------------------------

The example works for versions 3.3.x and 3.2.x (I haven't verified the rest).
It looks like the schema didn't change so I need to look into this a bit more.

[CLAassistant]

All committers have signed the CLA.

[lena-larionova]

LGTM!

Will have to update another time to add Redis descriptions as well, once I've got those ported over.