This patch adds support for filtering rows based on rules and values.
Filters will work for any attribute data source, they are a property
of the spreadsheet rather than of the attribute system. The properties
displayed in the row filter can depend on data type of the currently
visible column with that name. If the name is no longer visible, the
row filter filter is grayed out, but it will remember the value until
a column with its name is visible again.
Note: The comments in `screen.c` combined with tagging the sidebar
for redraw after the main region point to a lack of understanding
or technical debt, that is a point to improve in the future.
**Future Improvements**
* T89272: A search menu for visible columns when adding a new filter.
* T89273: Possibly a "Range" operation.
Differential Revision: https://developer.blender.org/D10959
A `DataSource` provides columns for the spreadsheet to display.
Every column has a SpreadsheetColumnID as identifier. Columns
are not generated eagerly anymore, instead the main spreadsheet
code can request a column from a data source with an column
identifier. The column identifiers can be stored in DNA and allow us
to store persistent data per column.
On the user level the only thing that changes is that columns are
not shown in alphabetical order anymore. Instead, new columns
are always added on the left. The behavior can be changed,
however I'd prefer not to automate this too much currently. I think
we should just add operators to hide/reorder/resize columns soonish.
Differential Revision: https://developer.blender.org/D10901
