This:

- brings consistency - no more mixing `_name_prefix` and `_registry_prefix`
- adds extensibility - a future patch will allow reconfiguring all registry prefixes for all roles in the playbook

We still have `_docker_` vs `_container_` inconsistencies.
These may be worked on later.

* Replace "Element" with "Element Web"

- If Element indicates the web application, then it is changed to Element Web.
- If it indicates clients branded with Element such as Element desktop, web, mobile clients, then it is changed to Element clients.
- If it is combined with location sharing functionality, it is not changed.

with other some changes, including:

- Change "app.element.io" anchor link to "https://github.com/element-hq/element-web" on README.md, following other documentation files

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

* Replace "SchildiChat" with "SchildiChat Web"

- If SchildiChat indicates the web application, then it is changed to SchildiChat Web.
- If it indicates clients branded with SchildiChat such as SchildiChat desktop, web, mobile clients, then it is changed to SchildiChat clients.
- If it is combined with location sharing functionality, it is not changed.

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

* Rename configuring-playbook-client-schildichat.md to configuring-playbook-client-schildichat-web.md

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

* Rename configuring-playbook-client-element.md to configuring-playbook-client-element-web.md

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

---------

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>
Co-authored-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

Ref:
- https://github.com/matrix-org/matrix-react-sdk/pull/12153
- https://github.com/element-hq/element-web/pull/26885

Technically, it may still work for Schildichat, because it's stuck in
the past. It will catch up soon anyway.

Putting each client into its own network was good for isolation,
but it's quite wasteful in terms of the container network pool.