[Gen AI] [Integrations] Add CEL input template

[bhapas]

Summary

This PR adds CEL input template in Integration Assistant Plugin under Data Collection method for data streams.

For maintainers

• This was checked for breaking API changes and was labeled appropriately

[bhapas]

@elasticmachine merge upstream

[bhapas]

/ci

[bhapas]

/ci

[kibana-ci]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: 01bfd98

Failed CI Steps

• FTR Configs #7

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
integrationAssistant	844.1KB	844.2KB	+60.0B

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

cc @bhapas

[elasticmachine]

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

[semd]

LGTM! Thanks @bhapas for adding this. I've tested the changes and it works well.