Why:
* The temporary account configuration settings, which are
controlled via wgAutoCreateTempUser have many options
and so defining the config for a test is difficult without
keeping a private array for the default array value.
* Providing methods to easily disable and enable temporary account
creation in a one-line call is useful to fix existing tests
for temporary account creation.
What:
* Add the trait named TempUserTestTrait which provides two methods
that disable and enable temporary account autocreation.
* This trait is designed for use in integration tests as it modifies
configuration values.
* The ::enableAutoCreateTempUser method optionally takes an array
that can be used to override the default wgAutoCreateTempUser
configuration.
* The ::disableAutoCreateTempUser method optionally takes a value
for the reservedPattern key as this is still used if the 'enabled'
key is set to false.
Bug: T352693
Change-Id: I21c5c7d61370b9ce96059341e0744abc61545e09
