[Canvas] Image Repeat element - the number of images becomes incorrect when the value changes

[hisashinz]

Kibana version: 7.12.0, 7.11.1, 7.10.2, 7.10.0

Elasticsearch version: 7.12.0, 7.11.1, 7.10.2, 7.10.0

Server OS version: ESS

Browser version: Firefox 87.0 (64 bit)

Browser OS version: macOS Big Sur 11.2.3

Original install method (e.g. download page, yum, from source, etc.): ESS

Describe the bug:
With the version > 7.10.0, the number of images is incorrect for a Canvas Image Repeat element when the value changes.

(Kibana 7.9.3 does not have the issue)

Steps to reproduce:

1. Load 'flight' data sample
2. Open the Canvas for the 'flight' sample.
3. Add an Image repeat element.
   4 Open the expression editor for the Image repeat element and replace the expression with the following.

filters 
| essql query="SELECT DestCountry as dest FROM kibana_sample_data_flights LIMIT 10" 
| math "unique(dest)" 
| repeatImage image={asset "asset-520a03a1-f522-4a18-ad4a-b84e87e4dc44"}
| render

5. Add a metric element.
6. Open the expression editor for the metric element and replace the expression with the following.

filters
| essql query="SELECT DestCountry as dest FROM kibana_sample_data_flights LIMIT 10"
| math "unique(dest)"
| formatNumber "0a]"
| metric 
 metricFont={font family="'Open Sans', Helvetica, Arial, sans-serif" size=60 align="right" color="#4184A5" weight="normal" underline=false italic=false} 
| render

7. Refresh the browser to reload the canvas.
8. Make sure the number of images and value shown in the metric is the same.
   (In the following picture, the number is 6. The metric element locates at the right side of the row of the images.)
   
9. Change the time span to make the number of the metrics to a different value.
   When it changes, the number of images that are shown will be wrong.
   (In the following picture, after time span was changed, the number in the metrics changes from 6 to 7, but the number of images is not 7)
   

Expected behavior:
At step 9, the number shown in the metric and the number of images should be the same.

[elasticmachine]

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

[elasticmachine]

Pinging @elastic/kibana-presentation (Team:Presentation)