[Security Solution] Exp flyout expandable widget rendering

[lgestc]

Summary

This tiny PR ensures that widget contents are not rendered until expanded (in the expandable flyout). This will
prevent unnecessary requests being sent when we open the flyout.

[lgestc]

@elasticmachine merge upstream

[lgestc]

@elasticmachine merge upstream

[christineweng]

Perhaps this comment is more applicable here :)

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: bf446c1

Metrics [docs]

Module Count

Fewer modules leads to a faster build time

id	before	after	diff
securitySolution	4240	4241	+1

Async chunks

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

id	before	after	diff
securitySolution	11.0MB	11.0MB	+462.0B

Unknown metric groups

ESLint disabled line counts

id	before	after	diff
enterpriseSearch	14	16	+2
securitySolution	410	414	+4
total			+6

Total ESLint disabled count

id	before	after	diff
enterpriseSearch	15	17	+2
securitySolution	489	493	+4
total			+6

History

• 💔 Build #139950 failed 1c11b42
• 💔 Build #139799 failed 955e26b
• 💛 Build #139438 was flaky 52ad499
• 💛 Build #139073 was flaky ef956a3
• 💔 Build #138845 failed 92cd7d8

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream