More fixes for functions (#503)

* add missing *args, **kwargs in WalkMapper.map_call

* memoize clone_for_callee

* remove default CombineMapper map_call implementation

* don't memoize map_function_definition in cached walk mappers

doesn't make sense, since it doesn't return anything

* support calls in InputGatherer

* make NamedCallResult compatible with attrs cache_hash=True

* enable cache_hash on FunctionDefinition

* enable calls in DirectPredecessorsGetter

* memoize Call creation

* make NamedCallResult.call a property

* remove redundant NamedCallResult.name (already defined in NamedArray)

* memoize NamedCallResult creation

* fix docstring

* remove non-argument placeholder check

now done in arraycontext

* fix equality for FunctionDefinition

* add FIXME

* attempt to fix doc warning

* don't construct NamedCallResult directly

* fix mapper method name in UsersCollector

* add FIXME

* Revert "add FIXME"

This reverts commit 72bf01daf4757c72560c5eaf937377b57ce6b07d.

* Revert "remove non-argument placeholder check"

This reverts commit 73478bc4ac16877f946ce868317d9d1d10fb2ca6.

* add some more missing *args, **kwargs to WalkMapper

* remove some unnecessary *args, **kwargs

* add get_func_def_cache_key to walk mappers to correctly handle function caching when extra arguments are present

* undo memoizing Call creation

* don't use regular dict for function call results

* fix type annotation for function result

* undo memoizing clone_for_callee

doesn't avoid retraversal when the same function is encountered inside the bodies of two different
functions

* add SizeParamGatherer.map_call

default map_call implementation was removed from CombineMapper, so it needs to be here

* Revert "add get_func_def_cache_key to walk mappers to correctly handle function caching when extra arguments are present"

This reverts commit 45eb68d54d6b0e74776fa9bde8d41c7f798b8c49.

* Revert "don't memoize map_function_definition in cached walk mappers"

This reverts commit c0e70cdc8821ae7b14c31acf38e996cdf6bd5896.