LVS: improve name() error message by including the name

[martinjankoehler]

Say we call name() with a pattern instead of a layer, we get the error below.

ERROR: In /Users/martin/Source/klayout-pex/pdk/ihp-sg13g2/libs.tech/kpex/sg13g2.lvs: 'name': First argument must be a layer
ERROR: RuntimeError: 'name': First argument must be a layer in Executable::execute
 /Users/martin/Source/klayout-pex/pdk/ihp-sg13g2/libs.tech/kpex/sg13g2.lvs:533:in 'block in LVS::LVSExecutable#execute'
 /Users/martin/Source/klayout-pex/pdk/ihp-sg13g2/libs.tech/kpex/sg13g2.lvs:532:in 'Array#each'
 /Users/martin/Source/klayout-pex/pdk/ihp-sg13g2/libs.tech/kpex/sg13g2.lvs:532:in 'LVS::LVSExecutable#execute'
 :/built-in-macros/lvs_interpreters.lym:31:in 'BasicObject#instance_eval'
 :/built-in-macros/lvs_interpreters.lym:31:in 'LVS::LVSExecutable#execute'

@klayoutmatthias Would be helpful to have the actual pattern included:

RuntimeError: 'name': First argument (somepattern) must be a layer in Executable::execute