[8.19] [Security Assistant] Responsive design for welcome screen (#226062)

[stephmilovic]

Backport

This will backport the following commits from main to 8.19:

• [Security Assistant] Responsive design for welcome screen (#226062)

Questions ?

Please refer to the Backport tool documentation

[elasticmachine]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: 31b8801

Failed CI Steps

• Jest Integration Tests #3

Metrics [docs]

Module Count

Fewer modules leads to a faster build time

id	before	after	diff
elasticAssistant	419	423	+4
integrationAssistant	538	542	+4
securitySolution	7527	7529	+2
total			+10

Async chunks

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

id	before	after	diff
securitySolution	9.4MB	9.4MB	-3.0B

Page load bundle

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

id	before	after	diff
elasticAssistant	263.0KB	264.1KB	+1.2KB