v6.2.2304: Merge branch 'i-tut-christoph' into 'master'

I tut christoph

See merge request ngsolve/ngsolve!1327

v6.2.2301

parallel diagonal assembling

v6.2.2204

lambda capture

v6.2.2203

update netgen for ngtcl

v6.2.2202

Update Netgen, fix netgen version in pip packages

v6.2.2201

pip - install netgen from real repository

v6.2.2105

Merge branch 'GradVectorL2Piola_ApplySIMDIR_curved' into 'master'

DiffOpGradVectorL2Piola ApplySIMDIR for curved elements

See merge request jschoeberl/ngsolve!1136

v6.2.2104

trace with averaging

v6.2.2103

update Netgen

v6.2.2102

Merge branch 'product_space_inherits_dgjumps' into 'master'

product sapce inherits dgjumps flags from comp.s

See merge request jschoeberl/ngsolve!1026