System tests for OTel policies must check that the default policy template name matches with the expected receiver

Follow up to https://github.com/elastic/kibana/issues/237145.

Default dataset for OTel inputs should be the same that would be used by the vanilla OTel collector with the community receiver.

This helps to integrate with content packages developed for the community receivers. For example the MySQL content package expects documents to contain `mysqlreceiver.otel` dataset (see [here](https://github.com/elastic/integrations/blob/50dfc4f09fbd145d67cfc9941f866e308cce1858/packages/mysql_otel/kibana/dashboard/mysql_otel-73691849-6ca6-461b-b37a-b8b0d7d3d0a5.json#L49)). So a possible mysql input package should have `mysqlreceiver` as policy template name:
```yaml
...
policy_templates:
- name: mysqlreceiver # <- This name is used as default dataset in input packages.
input: otelcol
...
```

Add a check to ensure that this name, and by this, the default dataset, corresponds to the one of the receiver.

Future integration packages for OTel will also need to take this into account (https://github.com/elastic/ingest-dev/issues/5713).

Start by locating the system tests for OTel policy templates and the handling of the `policy_templates` YAML, then compare each policy template name with its receiver. The work is done when the tests verify that the default dataset derived from the policy template matches the community receiver, including the `mysqlreceiver.otel` example.

Written by the indexing model from the issue text.