[SLO] Slo search definitions tests improvements

[mgiota]

This is a follow up PR to this one that improves tests and addresses:

• search_slo_definitions integration tests: no need to create SLOs for the test, since we rely only on summary documents. We can just insert a bunch of summary documents with various names, etc...
• search_slo_definitions unit tests: add some checks on the size > 0 && size <= 100

cc @kdelemme

[elasticmachine]

Pinging @elastic/obs-ux-management-team (Team:obs-ux-management)

[elasticmachine]

Pinging @elastic/actionable-obs-team (Team:actionable-obs)

[elasticmachine]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: 5d888fd

Failed CI Steps

• FTR Configs #27
• FTR Configs #126

Test Failures

• [job] [logs] FTR Configs #27 / Agent Builder converse Conversation Error Handling shows error message when there is an error and allows user to retry
• [job] [logs] FTR Configs #126 / integrations For each artifact list under management "before all" hook in "For each artifact list under management"

Metrics [docs]

✅ unchanged

History

• 💔 Build #386439 failed 120f7b3
• 💔 Build #386423 failed 3958369
• 💔 Build #386204 failed 44b7a19

cc @mgiota

[kdelemme]

LGTM, thanks for coming back to this