After the introduction of the BlockManager (T219441), move over methods on the Block class that belong there.

This includes helper methods for getting blocks that apply to a user, such as Block::chooseBlock.

It also includes methods that require knowledge of global configs, such as Block::appliesToUsertalk, which needs to know about $wgBlockAllowsUTEdit. This should be split between the BlockManager (to allow MultipleBlock (T206163) to handle the multiple block case). Other methods are similar to this.

This work will conflict with the Block refactor in T206163, and can be done afterwards.