Create Kamelet Definition Editor

[igarashitm]

Please describe the feature that you want to propose

Kamelet has extra metadata that other DSL doesn't have, but vital for Kamelet specification.
https://camel.apache.org/camel-k/1.12.x/apis/kamelets.html#_camel_apache_org_v1alpha1_KameletSpec

Definition

defines the formal configuration of the Kamelet
https://camel.apache.org/camel-k/1.12.x/apis/kamelets.html#_camel_apache_org_v1alpha1_JSONSchemaProps
Especially properties defined here
https://github.com/apache/camel-kamelets/blob/fe958c866ae29dd93887ec38298bd8ca1b32a5fb/kamelets/avro-deserialize-action.kamelet.yaml#L42
is referenced as a property placehoder in the template route
https://github.com/apache/camel-kamelets/blob/fe958c866ae29dd93887ec38298bd8ca1b32a5fb/kamelets/avro-deserialize-action.kamelet.yaml#L60

We need to provide a user assist to show those already defined properties as a candidate for the template route parameter value. One option is when user type {{, show candidates from existing properties. This feature will be re-used for generic property placeholder support across all DSLs, but only Kamelet has spec.definition.properties locally.
Other DSLs would depend on external property file, k8s configmap, etc.
The other way around also has a room to assist users, for example when user put property placeholder that doesn't exist, automatically create one in spec.definition.properties.

Types / DataTypes

data specification types for the events consumed/produced by the Kamelet
https://camel.apache.org/camel-k/1.12.x/apis/kamelets.html#_camel_apache_org_v1alpha1_EventTypeSpec
https://camel.apache.org/camel-k/next/apis/kamelets.html#_camel_apache_org_v1alpha1_DataTypesSpec

Types / DataTypes will be leveraged for Data Mapper in the future #253

Metadata schema endpoint

First migrate schema mockup in UI to the backend
#2160 (comment)