fix: actions menu for envelope

[madbob]

I've simplified a bit the management of actions menu in EnvelopeSkeleton, to handle the many involved conditions.

Notes:

• the ugly setTimeout in handleActionsUpdateOpen is to delay a bit the status change for the closed menu; without it, the flickering menu mentioned in Action menu flickers for some actions #12586 cannot be really fixed. I've already opened an issue for nextcloud-vue in order to have a proper way to manage this
• almost unrelated to the target issue - but still related to actions menu - are the changes in MessageHTMLBody. The (untracked) issue is that NcActions registers a global handler to intercept clicks made on whole document and determines if the opened menu has to be closed, but clicks occurring over the iframe of MessageHTMLBody are "absorbed" by the iframe itself and do not bubble to the rest of the document. This change is intended to pre-intercept those clicks and properly deliver them to that global callback: now action menus are closed also when clicking on the HTML body of an email (which often occupies the large portion of the screen). If those changes seem too unrelated to the scope of this PR, I can split them in a different dedicated PR
• wandering up and down EnvelopeSkeleton I've found a few props that are never set by anyone and I guess can be removed. forceDisplayActions has been here suppressed, while counterNumber and counterType are still there. The commit introducing them (0b15b42) provides no hints about their scope. If no-one has any suggestion about their meaning and intended usage, I can remove them within this same PR

Fixes #12586

[ChristophWurst]

Thanks! Will try to review soon 🤞

[madbob]

I've overwritten the previous commit, following the wise notices of @ChristophWurst

Highlights:

• removed the unused ref to mainCard, introduced by one of my previous tries and forgot in the code
• fixed e / event reference in handleBlur(): I have no idea how I missed that, as I tested it and it worked. Eventually I messed up everything moving code around
• entirely removed the @keydown.esc callback assignation, as it is already handled by NcActions and seems to be redundant here. Important note: I've tested keyboard navigation, but an extra validation by an accessibility-focused person would be really appreciated
• removed all changes to MessageHTMLBody, to be submitted in a dedicated PR

[madbob]

I've realized that EnvelopeSkeleton originated just as a copy&paste of NcListItem from @nextcloud/vue, and includes many properties and behaviors relevant for the generic NcListItem but never used in Mail.
This replies to my original question about counterNumber and similar.

After this PR is merged, a more comprehensive review would be required.

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