osc8: update URI ranges as we print data, *not* when the URI is closed

At first, an OSC-8 URI range was added when we received the closing
OSC-8 escape (i.e. with an empty URI).

But, this meant that cursor movements while the OSC-8 escape was in
effect wasn’t handled correctly, since we’d add a range that spanned
the cursor movements.

Attempts were made to handle this in the cursor movement functions, by
closing and re-opening the URI.

However, there are too many corner cases to make this a viable
approach. Scrolling is one such example, line-wrapping another.

This patch takes a different approach; emit, or update the URI range
when we print to the grid. This models the intended behavior much more
closely, where an active OSC-8 URI act like any other SGR attribute -
it is applied to all cells printed to, but otherwise have no effect.

To avoid killing performance, this is only done in the “generic”
printer. This means OSC-8 open/close calls must now “switch” the ASCII
printer.

Note that the “fast” printer still needs to *erase* pre-existing OSC-8
URIs.

Closes #816

CHANGELOG.md

@@ -48,6 +48,9 @@
 
 * An ongoing mouse selection is now finalized on a pointer leave event
   (for example by switching workspace while doing a mouse selection).
+* OSC-8 URIs in the last column
+* OSC-8 URIs sometimes being applied to too many, and seemingly
+  unrelated cells (https://codeberg.org/dnkl/foot/issues/816).
 
 
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