[8.9] [Fleet] Change default batch size (#161249)

[kibanamachine]

Backport

This will backport the following commits from main to 8.9:

• [Fleet] Change default batch size (#161249)

Questions ?

Please refer to the Backport tool documentation

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: fb97aeb

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
fleet	976.7KB	976.9KB	+215.0B

Unknown metric groups

ESLint disabled line counts

id	before	after	diff
enterpriseSearch	13	15	+2
securitySolution	415	419	+4
total			+6

Total ESLint disabled count

id	before	after	diff
enterpriseSearch	14	16	+2
securitySolution	496	500	+4
total			+6

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

cc @nchaulet