Avoid calling expensive sipConvertFromNewType method when feature
attribute is a trivial type
Also avoid a copy of the feature attributes which we don't require
This change is similar to the one introduced in the previous
commit for `QgsAttributes` . The python call of `setAttribute` expects
a `QVariant` as input. sip is able to directly handle `QVariant` but
this allocation can be slow.
In some cases, it is possible to speed-up the `setAttribute` call by
checking the type of the attribute. If the attribute is a boolean, an
integer, a float or a string, it is possible to avoid the intermediate
sip QVariant allocation done by `sipConvertToType`.
Based on some testing, this allows to speed-up a python `setAttribute`
call up to 80%. If the python attribute is already a `QVariant`, then
one get the same time.
The original workaround was only supposed to apply to QList/
QVector of QVariantMaps. By replacing them all in sip we
break mapping of signals defined in c++ which are emitted
by Python code.
Fixes exceptions after running processing algorithms in Qt6
builds.
