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.

* Rename variables matrix_bot_postmoogle_* with matrix_postmoogle_*

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

* Rename file names and references to those files

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

* Move variables block for /matrix-bridge-postmoogle

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

* Rename matrix_playbook_bot_postmoogle_ to matrix_playbook_bridge_postmoogle_

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

* Add matrix_playbook_migration_matrix_postmoogle_migration_validation_enabled

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

* Replace an install tag example with "-bot" prefix

The previous example seems to have been selected to show how components whose name contains "-bot-" needed to be specified.

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>