Add oik-loader-mu-reload action

[bobbingwide]

oik-unloader's [active_plugins] shortcode can update:

• list of plugins which are to be unloaded
• the list of plugins to be loaded.

oik-loader-mu is loaded before oik-unloader-mu When entries are removed from oik-loader-extras these updates need to applied in oik-loader-mu We need an oik-loader-mu-reload action hook invoked by oik-unloader that will cause oik-loader-mu to reload the arrays. This will then be reflected in the output of the active_plugins shortcode.

See https://github.com/bobbingwide/oik-unloader/issues/7#issuecomment-1046858333

[bobbingwide]

Delivered in oik-loader v1.4.0 and oik-unloader v0.2.0