[Security Solution] Fix incorrect number of alerts shows under External alert trend

[machadoum]

issue: #111679

Summary

During a previous fix, I broke the trend graph for External alerts. The reason is that I started counting the total of events based on the bucket. But every kind of MatrixHistogramType has a different aggregation name. eventActionGroup was wrongly hardcoded inside useMatrixHistogram. After this change, buckets should be returned for every type of MatrixHistogram.

132640542-440cd073-2c02-4277-8226-d2fd7c2ead8b.mp4

Checklist

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Unit or functional tests were updated or added to match the most common scenarios

[elasticmachine]

Pinging @elastic/security-solution (Team: SecuritySolution)

[elasticmachine]

Pinging @elastic/security-threat-hunting (Team:Threat Hunting)

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: db66aca
• Storybooks Preview

Metrics [docs]

Public APIs missing comments

Total count of every public API that lacks a comment. Target amount is 0. Run node scripts/build_api_docs --plugin [yourplugin] --stats comments for more detailed information.

id	before	after	diff
securitySolution	1285	1292	+7

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
securitySolution	6.5MB	6.5MB	+36.0B

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
securitySolution	207.7KB	208.4KB	+778.0B

Unknown metric groups

API count

id	before	after	diff
securitySolution	1338	1345	+7

History

• 💔 Build #152285 failed 7d9b4b9

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cc @machadoum

[kibanamachine]

💚 Backport successful

Status	Branch	Result
✅	7.15
✅	7.x

The backport PRs will be merged automatically after passing CI.