[Redis Enterprise] Add mapping metric_type mapping for the fields of node datastream

[ritalwar]

Proposed commit message

This PR adds the metric_type mapping for the fields of node datastream of Redis Enterprise.

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.
• I have verified that Kibana version constraints are current according to guidelines.

Related issues

• Relates [Redis Enterprise] TSDB Enablement #6268

Screenshots

[elasticmachine]

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• Start Time: 2023-11-18T07:48:27.918+0000

• Duration: 19 min 24 sec

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Test	Results
Failed	0
Passed	5
Skipped	0
Total	5

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[agithomas]

LGTM!

[elasticmachine]

🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (0/0)	💚
Files	100.0% (0/0)	💚 3.851
Classes	100.0% (0/0)	💚 3.851
Methods	50.0% (4/8)	👎 -42.243
Lines	100.0% (0/0)	💚 11.556
Conditionals	100.0% (0/0)	💚

[harnish-elastic]

LGTM!

[elasticmachine]

Package redisenterprise - 0.8.1 containing this change is available at https://epr.elastic.co/search?package=redisenterprise