Refactored `Site.expandtemplates` to use the updated API, addressing
deprecation warnings in recent MediaWiki versions.

The older API triggered the following warnings:

```
WARNING:mwclient.client:Subscribe to the mediawiki-api-announce mailing list at <https://lists.wikimedia.org/postorius/lists/mediawiki-api-announce.lists.wikimedia.org/> for notice of API deprecations and breaking changes. Use [[Special:ApiFeatureUsage]] to see usage of deprecated features by your application.
WARNING:mwclient.client:The parameter "generatexml" has been deprecated.
Because "prop" was not specified, a legacy format has been used for the output. This format is deprecated, and in the future the new format will always be used.
```

This adds an integration test that runs a set of mediawiki
containers, configures them enough that the API works, then runs
a few simple tests of logging in, creating, moving and deleting
pages. We also enable this in CI. We can extend this with more
tests later, I think this is a reasonable initial set.

Signed-off-by: Adam Williamson <awilliam@redhat.com>