[8.12] fix(slo): add defer validation to transforms (#174463) (#174519)

# Backport

This will backport the following commits from `main` to `8.12`:
- [fix(slo): add defer validation to transforms
(#174463)](#174463)

<!--- Backport version: 8.9.8 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sqren/backport)

<!--BACKPORT [{"author":{"name":"Kevin
Delemme","email":"kevin.delemme@elastic.co"},"sourceCommit":{"committedDate":"2024-01-09T13:20:09Z","message":"fix(slo):
add defer validation to transforms
(#174463)","sha":"5bdb5d826ef869fffef4c6200236aa69109b4c3b","branchLabelMapping":{"^v8.13.0$":"main","^v(\\d+).(\\d+).\\d+$":"$1.$2"}},"sourcePullRequest":{"labels":["release_note:fix","backport:prev-minor","Feature:SLO","v8.12.0","Team:obs-ux-management","v8.13.0"],"number":174463,"url":"https://github.com/elastic/kibana/pull/174463","mergeCommit":{"message":"fix(slo):
add defer validation to transforms
(#174463)","sha":"5bdb5d826ef869fffef4c6200236aa69109b4c3b"}},"sourceBranch":"main","suggestedTargetBranches":["8.12"],"targetPullRequestStates":[{"branch":"8.12","label":"v8.12.0","labelRegex":"^v(\\d+).(\\d+).\\d+$","isSourceBranch":false,"state":"NOT_CREATED"},{"branch":"main","label":"v8.13.0","labelRegex":"^v8.13.0$","isSourceBranch":true,"state":"MERGED","url":"https://github.com/elastic/kibana/pull/174463","number":174463,"mergeCommit":{"message":"fix(slo):
add defer validation to transforms
(#174463)","sha":"5bdb5d826ef869fffef4c6200236aa69109b4c3b"}}]}]
BACKPORT-->

x-pack/plugins/observability/server/assets/transform_templates/slo_transform_template.ts

@@ -48,6 +48,7 @@ export const getSLOTransformTemplate = (
     group_by: groupBy,
     aggregations,
   },
+  defer_validation: true,
   _meta: {
     version: SLO_RESOURCES_VERSION,
     managed: true,

x-pack/plugins/observability/server/services/slo/summary_transform_generator/generators/occurrences.ts

@@ -127,6 +127,7 @@ export function generateSummaryTransformForOccurrences(slo: SLO): TransformPutTr
       deduce_mappings: false,
       unattended: true,
     },
+    defer_validation: true,
     _meta: {
       version: SLO_RESOURCES_VERSION,
       managed: true,

x-pack/plugins/observability/server/services/slo/summary_transform_generator/generators/timeslices_calendar_aligned.ts

@@ -157,6 +157,7 @@ export function generateSummaryTransformForTimeslicesAndCalendarAligned(
       deduce_mappings: false,
       unattended: true,
     },
+    defer_validation: true,
     _meta: {
       version: SLO_RESOURCES_VERSION,
       managed: true,

x-pack/plugins/observability/server/services/slo/summary_transform_generator/generators/timeslices_rolling.ts

@@ -129,6 +129,7 @@ export function generateSummaryTransformForTimeslicesAndRolling(
       deduce_mappings: false,
       unattended: true,
     },
+    defer_validation: true,
     _meta: {
       version: SLO_RESOURCES_VERSION,
       managed: true,