[BUG] host.domain is being reported but endpoint-package does does not contain it

We are adding `host.domain` in common for all ECS code https://github.com/elastic/endpoint-dev/blob/ea6662b8d5290bee673b70edf44c94e894b7a9af/Libraries/ECS/Lib/ECS.cpp#L376-L379
but the corresponding package documentation does not exist:
https://github.com/elastic/endpoint-package/blob/2e5f67745669bec46a62ece6777e796f1be7847d/custom_documentation/src/endpoint/data_stream/metadata/metadata.yaml#L49-L50
https://github.com/elastic/endpoint-package/blob/2e5f67745669bec46a62ece6777e796f1be7847d/custom_documentation/src/endpoint/data_stream/metrics/metrics.yaml#L219-L220
https://github.com/elastic/endpoint-package/blob/2e5f67745669bec46a62ece6777e796f1be7847d/custom_documentation/src/endpoint/data_stream/policy/policy_response.yaml#L98-L99
https://github.com/elastic/endpoint-package/blob/2e5f67745669bec46a62ece6777e796f1be7847d/custom_documentation/src/endpoint/data_stream/alerts/windows/windows_malicious_behavior_alert.yaml#L82-L83

Start by reading the host.domain definition in Libraries/ECS/Lib/ECS.cpp, then inspect the referenced metadata.yaml, metrics.yaml, policy_response.yaml, and windows_malicious_behavior_alert.yaml files. Add the missing host.domain documentation consistently to all four locations; done means each corresponding package document describes the field.

Written by the indexing model from the issue text.