Add IP* fields to fields.yml generator script (#18256)

## What does this PR do?

This PR adds the following patterns to the fields.yml generator with the type `ip`:
- `IP`
- `IPV4`
- `IPV6`

## Why is it important?

From now on `fields.yml` generator is able to guess the correct type for fields which match the patterns mentioned above.

CHANGELOG-developer.next.asciidoc

@@ -86,3 +86,4 @@ The list below covers the major changes between 7.0.0-rc2 and master only.
 - Add support for MODULE environment variable in `mage goIntegTest` in metricbeat to run integration tests for a single module. {pull}17147[17147]
 - Add support for a `TEST_TAGS` environment variable to add tags for tests selection following go build tags semantics, this environment variable is used by mage test targets to add build tags. Python tests can also be tagged with a decorator (`@beat.tag('sometag')`). {pull}16937[16937] {pull}17075[17075]
 - Add fields validation for histogram subfields. {pull}17759[17759]
+- Add IP* fields to `fields.yml` generator script in Filebeat. {issue}17998[17998] {pull}18256[18256]

filebeat/generator/fields/fields.go

@@ -45,6 +45,9 @@ var (
 		"GREEDYDATA":      "text",
 		"GREEDYMULTILINE": "text",
 		"HOSTNAME":        "keyword",
+		"IP":              "ip",
+		"IPV4":            "ip",
+		"IPV6":            "ip",
 		"IPHOST":          "keyword",
 		"IPORHOST":        "keyword",
 		"LOGLEVEL":        "keyword",