If not, mIsChanged state and multiedit button icon are not updated in
QgsAttributeFormEditorWidget. The former leads to not saving
modification issues when applying multi edit modifications because
widget could appear not changed.

When closing a 2D canvas dock, QGIS sometimes crashes. This is because
when the widget helper is closed, the canvas is closed. However, some
signals of the canvas widget may still be called after it is
called. Hence, the crash.

This issue is fixed by calling `deleteLater()` instead of `delete` to
ensure a proper deletion which properly takes into account the
signals.

We were incorrectly showing the "transformed" coordinate result
in the exception message, which usually ended up inf, inf after
the transform fails. This lead to a useless 'forward transform of
(inf, inf)' message in the exception, which was misleading
as it looks like we were trying to transform a (inf, inf) point.

Now we get the (useful!) actual coordinate we were trying
to transform in the exception message.

(cherry picked from commit c8d25f6)

…on't need to

(cherry picked from commit 276cbec)

The old code mistakenly assumed that proj error codes were all
values < 0, which they haven't been since proj 8.0

This meant all QgsCsExceptions were incorrectly including
"Error: Fallback transform failed", instead of the actual
error message from proj.

Now we get eg "Forward transform of (-7603859.000000, -7324441.000000)
Error: Invalid coordinate", which makes much more sense

(cherry picked from commit 00c7268)

(cherry picked from commit 16de21a)

Eg:

    Forward transform (EPSG:4326 to EPSG:3857) of
    (-7603859.000000, -7324441.000000) Error: Invalid coordinate

(cherry picked from commit 9b69caf)

(cherry picked from commit b682d36)

(cherry picked from commit 5733e3d)

(cherry picked from commit a390b40)

(cherry picked from commit ba07d87)

(cherry picked from commit 93bce2e)

(cherry picked from commit 6ec289d)

(cherry picked from commit a6a18a9)

(cherry picked from commit f7e1550)

(cherry picked from commit 60780fc)