[Ingest Pipelines] Unable to add multiple patterns in grok processor

[alisonelizabeth]

Kibana version:
8.1

Describe the bug:
The grok processor "pattern" input is not working as expected.

Steps to reproduce:

1. Navigate to Ingest Node Pipelines --> Create pipeline
2. Add a new processor --> Select "Grok"
3. Add field name
4. Add a pattern, i.e., "test 1"
5. Add a second pattern, i.e., "test 2".
6. Click "Add pattern" to add a third pattern. Note the second pattern gets cleared.

Expected behavior:
The user should be able to add >1 grok patterns.

[elasticmachine]

Pinging @elastic/platform-deployment-management (Team:Deployment Management)

[alisonelizabeth]

This issue should be resolved by #128489, although we should add tests for the grok processor to validate.