Fix #1808: empty x-descriptors field and dataTypes empty default

[gansheer]

Ref #1814
Ref #1808

Some leftover errors on main branch:

amel-k-operator-77bf96b5b6-k9xc5 camel-k-operator {"level":"error","ts":"2023-12-21T16:20:42Z","msg":"Error occurred whilst applying bundled kamelet","error":"Kamelet.camel.apache.org \"aws-timestream-query-sink\" is invalid: [spec.definition.properties.useDefaultCredentialsProvider.x-descriptors: Invalid value: \"null\": spec.definition.properties.useDefaultCredentialsProvider.x-descriptors in body must be of type array: \"null\", spec.definition.properties.overrideEndpoint.x-descriptors: Invalid value: \"null\": spec.definition.properties.overrideEndpoint.x-descriptors in body must be of type array: \"null\"]","stacktrace":"github.com/apache/camel-k/v2/pkg/install.KameletCatalog.func1.1\n\tgithub.com/apache/camel-k/v2/pkg/install/kamelets.go:127\ngolang.org/x/sync/errgroup.(*Group).Go.func1\n\tgolang.org/x/sync@v0.5.0/errgroup/errgroup.go:75"}
camel-k-operator-77bf96b5b6-k9xc5 camel-k-operator {"level":"error","ts":"2023-12-21T16:20:43Z","msg":"Error occurred whilst applying bundled kamelet","error":"Kamelet.camel.apache.org \"google-sheets-source\" is invalid: spec.dataTypes.default: Invalid value: \"null\": spec.dataTypes.default in body must be of type object: \"null\"","stacktrace":"github.com/apache/camel-k/v2/pkg/install.KameletCatalog.func1.1\n\tgithub.com/apache/camel-k/v2/pkg/install/kamelets.go:127\ngolang.org/x/sync/errgroup.(*Group).Go.func1\n\tgolang.org/x/sync@v0.5.0/errgroup/errgroup.go:75"}

@christophd Please don't hesitate to indicate if dataTypes default: should be some other value.