Add includeFields parameter to the method extractFieldNamesTypes

[gaobinlong]

Description

This is a follow-up PR of #348, in that PR, we moved and refactored the method extractFieldNamesTypes, but the new method has some impact on the PPLTool, in order to remove the impact, this PR add a new parameter includeFields to that method, when it's set to false, the subfields under a text type field will not be resolved and written to the result.

For example, this is a text type field with subfields:

"c": {
      "type": "text",
      "fields": {
        "d": {
          "type":"keyword"
        }
      }
    }

, if includeFields is true, the flattened mapping result contains:

"c": "text",
"c.d": "keyword"

, but if includeFields is false, the flattened mapping result only contains:

"c": "text",

.

In addition, for object field, we do not extract the top level field name and type into the final result since it's useless for both PPLTool and CreateAnomalyDetectorTool actually.
For example, this is an object field with setting type explicitly:

"a": {
      "type": "object",
      "properties": {
        "b": {
          "type":"keyword"
        }
      }
    }

, the flattened mapping result contains:

"a.b": "keyword"

, but doesn't contain:

"a": "object"

.

Related Issues

Resolves #[Issue number to be closed when this PR is merged]

Check List

• New functionality includes testing.
• New functionality has been documented.
• API changes companion pull request created.
• Commits are signed per the DCO using --signoff.
• Public documentation issue/PR created.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[gaobinlong]

@zane-neo @xinyual please help to review this PR, thanks!