[Discover] Error handling when failed to build a search request

[Dosant]

Kibana version: 7.14 / master
Description of the problem including expected versus actual behavior:

Building a search request could fail for multiple reasons, mostly due to unsupported configuration.
For example #103082, the failure happens at:

kibana/src/plugins/discover/public/application/apps/main/services/use_saved_search.ts

Line 188 in 771f7de

searchSource.setField('aggs', chartAggConfigs.toDsl());

kbn-ui-shared-deps.js:298 Uncaught Error: Saved field "variants.updated" of index pattern "hc-products" is invalid for use with the "Date Histogram" aggregation. Please select a new field.
    at FieldParamType.write (field.ts:77)
    at agg_params.ts:48
    at Array.forEach (<anonymous>)
    at writeParams (agg_params.ts:46)
    at AggConfig.write (agg_config.ts:168)
    at AggConfig.toDsl (agg_config.ts:225)
    at agg_configs.ts:222
    at Array.forEach (<anonymous>)
    at AggConfigs.toDsl (agg_configs.ts:201)
    at use_saved_search.ts:126

In this example, Discover doesn't show the user an error. Even no toast.
It just continues to look like it is running a search:

** Expected behaviour **:

Exit loading state and show error an error state

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)