Refactor upload dialog to make it configurable

This aims to solve all the problems and fulfill all the use cases.
It allows the dialog to be configured for Wikimedia Commons without
hardcoding anything, and it should be flexible enough for third-party
use. The default configuration should be sane for any wiki.

The file upload dialog can be configured using $wgUploadDialog.
See DefaultSettings.php for documentation. Example configuration for
Wikimedia Commons: Id56370e2334c8fe34e88180356232b48c244b7c4.

Configuration is loaded using ResourceLoaderUploadDialogModule for
local uploads or using ApiQuerySiteinfo (action=query&meta=siteinfo)
for uploads to a foreign wiki. Custom localisation messages may be
loaded using action=query&meta=allmessages.

Renamed messages:

upload-form-label-own-work-message-local       -> upload-form-label-own-work-message-generic-local
upload-form-label-not-own-work-message-local   -> upload-form-label-not-own-work-message-generic-local
upload-form-label-not-own-work-local-local     -> upload-form-label-not-own-work-local-generic-local
upload-form-label-own-work-message-default     -> upload-form-label-own-work-message-generic-foreign
upload-form-label-not-own-work-message-default -> upload-form-label-not-own-work-message-generic-foreign
upload-form-label-not-own-work-local-default   -> upload-form-label-not-own-work-local-generic-foreign

Deleted messages, moved to WikimediaMessages in Id2977e19330aeaf854157d4355cd17e5dc72f16a:

upload-form-label-own-work-message-shared
upload-form-label-not-own-work-message-shared
upload-form-label-not-own-work-local-shared

Bug: T118097
Bug: T120998
Bug: T121632
Bug: T121633
Bug: T127895
Change-Id: I3017b8f09c27625deb7a92d6f667895b71cc0637