Support YAML completion for different hierarchy syntaxes

Is your enhancement related to a problem? Please describe.

Currently, I'm frustrated because completion does not work for these both cases:

level1:
  level2:

or:

level1.level2:

In one case, I have completion, but not in second case (or the opposite, up to schema definition).

Describe the solution you would like

it would be great if completion engine can consider these two syntaxes as the same, and so, provide the same completion.

To be more concrete, it would be great that this schema definition brings completion for both syntaxes:

      {
        "level1": {
          "type": "object",
          "properties": {
            "level2": {
              "type": "string"
            }
          }
        }
      }

Start by tracing the YAML completion engine's handling of nested indentation and dot-separated keys against the provided schema. Compare completion for both snippets, then verify that both hierarchy syntaxes produce the same schema-based suggestions.