[NcField] [NcSelect] field in forms

This came up recently in https://github.com/nextcloud-libraries/nextcloud-vue/pull/7838#issuecomment-4238313817, a little while ago in https://github.com/nextcloud/talk-desktop/pull/1530#issuecomment-3563283763, and https://github.com/nextcloud/server/pull/59431 which is still open.

It's clear that we want a way to more easily fit inputs into forms.

I'm proposing to adapt a solution similar to Talk Desktop:

For fields, a pencil icon would indicate that the field is editable. After clicking it, the "button" would be swapped out by an actual NcField, matching the styling and metrics of the button. Clicking on the checkmark would "save" the value and bring back the button.

For selects, it would be a similar story. Clicking on the button would swap it out with an expanded NcSelect of the same proportions, collapsing it would swap it back.

#7838 may still be viable for simpler selects, but we agreed that it isn't useful for everything, so we'd still need something like this.

What do you think @susnux @ShGKme @nimishavijay?

Start by reviewing the linked nextcloud-vue, Talk Desktop, and server pull requests, then inspect the existing NcField and NcSelect components. Clarify the interaction, component API, and styling requirements with the issue participants before implementation. Done means an agreed and working editable-field and select experience that matches the stated form proportions.