* Moves save/load into CardBrowserColumn
* Use the enum values, rather than the indices

Prep for Issue 11889

Breaking!
Updates the default columns from:

* QUESTION, ANSWER
to
* Cards: [Sort Field, Card Type, Due, Deck]
* Notes: [Sort Field, Note Type, Card Type/Type Count, Tags]

----

improvements:
* Support different columns for CARDS and NOTES mode
* Support more than 2 columns (not yet usable in the UI)

deprecates + upgrades shared prefs:
* "cardBrowserColumn1" - index into `COLUMN1_KEYS`
* "cardBrowserColumn2" - index into `COLUMN2_KEYS`

now (shared prefs):

* "activeCols" -> `|` separated list of column keys
* "activeNoteCols" -> `|` separated list of column keys

Prep for Issue 11889

For use in browserRowForId

Prep for Issue 11889

removes strings:
* browser_column1_headings
* browser_column2_headings

Prep for Issue 11889

unnecessary logging from logs of 'setColumn[1/2]'