When installing integrations, Fleet creates templates with index patterns following the indexing strategy: <type>-<dataset>-*

In the APM package, the datasets defined are only a prefix, and a service name will be appended during runtime. We therefore need that the APM templates are created with matching index patterns, like <type>-<dataset>*-*

Fleet should know whether to create templates with this alternative index pattern based on the dataset_is_prefix boolean field in the data stream manifest file.

Spec PR: elastic/package-spec#102