[aws] Add missing fields definition for ec2 data stream

[kaiyan-sheng]

What does this PR do?

1. add missing fields definitions into fields.yml for ec2 data stream
2. fix ec2 dashboard to use the correct field name

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.

[elasticmachine]

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Build stats

• Start Time: 2023-08-21T14:17:37.846+0000

• Duration: 56 min 39 sec

Test stats 🧪

Test	Results
Failed	0
Passed	208
Skipped	4
Total	212

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (17/17)	💚
Files	94.444% (17/18)	👍
Classes	94.444% (17/18)	👍
Methods	85.953% (257/299)	👍
Lines	86.024% (7509/8729)	👍
Conditionals	100.0% (0/0)	💚

[constanca-m]

/test

[elasticmachine]

Package aws - 1.53.3 containing this change is available at https://epr.elastic.co/search?package=aws