UTC and fixed interval not enforced for rolled up time series indices

[flash1293]

Kibana version: main

Describe the bug: In

kibana/src/plugins/data/common/search/aggs/buckets/date_histogram.ts

Line 223 in 9799dbb

const shouldForceFixedInterval: boolean = agg.params.field?.meta?.fixed_interval?.length;

it checks for this using field.meta.fixed_interval

But that's undefined

However on the spec, it is set.

Steps to reproduce:

1. Configure rolled up timeseries index
2. Build Lens or agg based chart on it with date histogram on the main time field
3. Observe requests are using local time zone and calendar interval

Expected behavior:
Should use fixed interval and UTC timezone

Screenshots (if relevant):

Errors in browser console (if relevant):

Provide logs and/or server output (if relevant):

Any additional context:

[elasticmachine]

Pinging @elastic/kibana-app-services (Team:AppServicesSv)