[Fleet] Using a * as the first character in a password throws a YAML validation error in the policy editor

[kpollich]

To reproduce

1. Create a package policy for the elasticsearch integration
2. Add a password beginning with * to the auth section under advanced options
3. Observe the validation error in the toast that appears

This looks like an issue with policy compilation or YAML validation in some capacity. We've seen similar issues with special character in passwords before, which I believe we've solved by wrapping fields in single quotes, e.g. #127268

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)

[kpollich]

The Elasticsearch integration needs to wrap its password fields in escape_string

https://github.com/elastic/integrations/blob/main/packages/elasticsearch/data_stream/node/agent/stream/stream.yml.hbs#L10-L15

Closing as this can be fixed on the integration side.