[Security solution] Rename Generative AI connector to OpenAI

[stephmilovic]

Redo this PR because this PR merged shortly before broke it and I had to fix an import

[elasticmachine]

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

[elasticmachine]

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

[jbudz]

This was already passing CI in #167519. One commit was added to fix a merge timing conflict with an import 674a095.

I've verified this is fixed, merging now.

[kibana-ci]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: 7557251

Failed CI Steps

• FTR Configs #2

Test Failures

• [job] [logs] FTR Configs #2 / Serverless Common UI - Management Indices "before all" hook for "renders the indices tab"

Metrics [docs]

Async chunks

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

id	before	after	diff
observabilityAIAssistant	199.9KB	199.9KB	-20.0B
securitySolution	12.8MB	12.8MB	+20.0B
stackConnectors	485.5KB	485.5KB	-33.0B
total			-33.0B

Page load bundle

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

id	before	after	diff
actions	15.9KB	15.9KB	+26.0B
stackConnectors	37.8KB	37.8KB	-5.0B
total			+21.0B

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