[memcached] Add dimension fields to stats datastream

[agithomas]

• Enhancement

What does this PR do?

Add dimension fields for stats datastream

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

#6925

Screenshots

[elasticmachine]

💚 Build Succeeded

the below badges are clickable and redirect to their specific view in the CI or DOCS

Expand to view the summary

Build stats

• Start Time: 2023-07-12T10:51:17.778+0000

• Duration: 15 min 57 sec

Test stats 🧪

Test	Results
Failed	0
Passed	4
Skipped	0
Total	4

🤖 GitHub comments

Expand to view the GitHub comments

To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.

[elasticmachine]

🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (0/0)	💚
Files	100.0% (0/0)	💚
Classes	100.0% (0/0)	💚
Methods	75.0% (3/4)	❕
Lines	100.0% (0/0)	💚
Conditionals	100.0% (0/0)	💚

[ritalwar]

LGTM!

[elasticmachine]

Package memcached - 1.1.0 containing this change is available at https://epr.elastic.co/search?package=memcached