## Summary
Closes#90454
Closes https://github.com/elastic/kibana/issues/72959
* Rename the component templates which are [installed for some packages](https://github.com/elastic/kibana/blob/master/x-pack/plugins/fleet/server/services/epm/elasticsearch/template/install.ts#L197-L213) from `${templateName}-mappings` and `${templateName}-settings` to `${templateName}@mappings` and `${templateName}@settings`
* When any package is installed, add a component template named `${templateName}@custom`
* Any of above templates also include a `_meta` property with `{ package: { name: packageName } }`
* On package installation, add any installed component templates to the `installed_es` property of the `epm-packages` saved object
* On package removal, remove any installed component templates from the `installed_es` property of the `epm-packages` saved object
<details><summary>Kibana logs showing component templates added for package</summary>
```
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [logs-endpoint.events.file@mappings]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [logs-endpoint.events.registry@mappings]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [.logs-endpoint.diagnostic.collection@mappings]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [logs-endpoint.events.library@mappings]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [logs-endpoint.events.security@mappings]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [logs-endpoint.events.network@mappings]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [logs-endpoint.alerts@mappings]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [metrics-endpoint.metrics@mappings]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [logs-endpoint.events.process@mappings]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [metrics-endpoint.policy@mappings]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [metrics-endpoint.metadata@mappings]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [logs-endpoint.events.registry@custom]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [.logs-endpoint.diagnostic.collection@custom]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [logs-endpoint.events.security@custom]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [logs-endpoint.events.file@custom]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [logs-endpoint.events.library@custom]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [logs-endpoint.events.network@custom]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [logs-endpoint.alerts@custom]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [metrics-endpoint.metrics@custom]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [metrics-endpoint.policy@custom]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [logs-endpoint.events.process@custom]
│ info [o.e.c.m.MetadataIndexTemplateService] [JFSIII.local] adding component template [metrics-endpoint.metadata@custom]
```
</details>
<details><summary>screenshot - component templates are editable in the Stack Management UI</summary>
<img width="1342" alt="Screen Shot 2021-06-17 at 4 06 24 PM" src="https://user-images.githubusercontent.com/57655/122465421-1502bb80-cf86-11eb-94f4-9880cb3ea844.png">
</details>
### Checklist
Delete any items that are not applicable to this PR.
- [ ] [Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html) was added for features that require explanation or tutorials
- [x] [Unit or functional tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html) were updated or added to match the most common scenarios
* Remove endpoint from the default packages
* Change the default spinner for the initial load
* Export fleet endpoint package as a constant
* Use constants for special packages
* Simplify type signature of `isRequiredPackage`
* Remove unused types
* Simplify required and default package definitions
* Treat REQUIRED_PACKAGES as independent from DEFAULT_PACKAGES
We want to keep the assumption that the lists contain the same packages
only in `epm/constants.ts`
* Install all default packages, not only the required ones
* Document the purpose of each package list
* Handle auto-update for non-default packages
* Make `endpoint` non-removable
* Make endpoint package be installed by default in tests
* Rename requiredPackages to unremovablePackages
* Fix type check
* Add Endpoint to be installed by default on Fleet tests too
Co-authored-by: Jen Huang <its.jenetic@gmail.com>
