Asset Browser: Filter options for specific ID types

Adds a filter popup to the header that allows specifiying which data-block
types to show. The menu automatically reflects all supported ID types, so it
shows a checkbox for materials, worlds and actions currently by default, and
all ID types with the "Extended Asset Browser" experimental feature enabled.

UI: Correct icons of File Browser Link/Append ID filter settings

Wasn't using the same icons as usually used for these IDs, which can be
confusing. Corrected them to be consistent with other usages of these IDs.

UI: Show ID filter settings in Link/Append File Browser as icon & checkbox

The checkboxes integrate better with the surrounding layout and are not that
attention grabbing. To my knowledge the only reason not to use checkboxes was
so the icons could be displayed. But this does it just like the Outliner filter
settings: Show the icon before the checkbox.

Also widen the popover a bit to fit longer labels (didn't fit before this patch
even).

Assets: Allow specific data-block types to be enabled by default

Updates UI code so that we can enable the asset UI for specific data-block
types by default, i.e. irrespective of the "Extended Asset Browser"
experimental feature.
"Mark as Asset" and "Clear Asset" are always visible in the Outliner context
menu now, but are grayed out if not applicable and show a disabled hint in the
tooltip.

A known side-effect of this: The "Mark as Asset" and "Clear Asset" operators
are enabled for action data-blocks now, even though only pose actions created
through the Pose Libraries add-on are supported. If this is something worth
addressing is being discussed still.

Differential Revision: https://developer.blender.org/D12955

Reviewed by: Sybren Stüvel

Assets: Enable material and world assets by default

Both material and world assets should be ready to use as non-experimental
feature. They were not enabled by default yet because the work from the
previous commit was needed first.
Objects should follow soon.

Maniphest Task: https://developer.blender.org/T91752

Fix tooltip disabled hint not using correct context from the button

To display the "disabled hint" (text explaining why a button is disabled) in a
tooltip, it would run the operator poll callback, which could then set a poll
message. But the context for the poll check wasn't the one from the button, so
the poll may give a different result (and disabled hint) than the check of the
button itself did.
Make sure it uses the exact context from the button.

Fix T92368: LMB mouse events (Selecting, doubleclicks etc) are broken

Asset Browser: Show current file assets in other asset libraries if contained

If the current file is saved within an asset library, showing that asset
library in the Asset Browser will also display the assets from this current
file now. In fact, it's the latest state of the open file, including all
unsaved modifications.
These assets will show a little Blender icon in the preview image, which is our
usual icon for current file data.

Note that this means an important design change: The "Current File" asset
library isn't the only place to edit assets from anymore. From now on assets
from the current file can also be edited in the context of the full asset
library. See T90193 for more info.

Technical info:
Besides just including the assets from the current `Main`, this requires
partial clearing and reading of file-lists, so that asset operations (e.g.
removing an asset data-block) doesn't require a full reload of the asset
library.

Maniphest Task: https://developer.blender.org/T90193

Cleanup: Remove unused file-list array info members

UI: Activate parent when active child is collapsed

Previously, when an item was active and its parent (or grand parent, etc.) was
collapsed, the active item would simply not be visible anymore. It seemed like
there was no active item. So instead, change the just collapsed parent to be
the active item then, so the active item stays visible.