[IMP] mail: message action registry + reorder actions in inbox

[phenix-factory]

Before this commit, message actions were all defined in template
of Message component. It's good when there are few actions and
the ordering of actions is always the same, but there are now
many actions and we want to order these actions depending on context.

This commit fixes the issue by introducing a special registry to add
message actions. This registry is quite similar to thread actions:
each item define conditions to be shown, behaviour on click, and
their sequence which can depend on the context where the message is
being viewed.

In addition to this message action registry, this commit also
reorder message actions in inbox as follow:

1. Quick actions:

• Add a Reaction
• Mark as To do
• Mark as Read

2. More menu:

• View reactions
• Reply
• Unfollow
• Edit
• Delete

Task-3458086

[robodoo]

[alexkuhn]

I would introduce message_actions with a similar architecture to thread_actions, so that it's much easier to adapt for new specs