Make gimple_build main workers more flexible

The following makes the main gimple_build API take a
gimple_stmt_iterator, whether to insert before or after and
an iterator update argument to make it more convenient to use
in certain situations (see the tree-vect-generic.cc hunks for
an example).  It also makes the case we insert into the IL
somewhat distinct from inserting into a standalone sequence in
that it simplifies built expressions the same way as inserting
and calling fold_stmt (..., follow_all_ssa_edges) would.  When
inserting into a standalone sequence we restrict simplification
to defs within the currently building sequence.

The patch only amends the tree_code gimple_build API, I will
followup with converting the rest as well.  The patch got larger
than intended because the template forwarders now use gsi_last
which introduces a dependency on gimple-iterator.h requiring
mass #include re-org across the tree.  There are two frontend
specific files including gimple-fold.h just for some padding
clearing stuff - I've removed the include and instead moved
the declarations to fold-const.h (but not the implementations).
Otherwise I'd have to include half of the middle-end headers in
those files which I didn't much like.

2022-05-12  Richard Biener  <rguenther@suse.de>

gcc/cp/
	* constexpr.cc: Remove gimple-fold.h include.

gcc/c-family/
	* c-omp.cc: Remove gimple-fold.h include.

gcc/analyzer/
	* supergraph.cc: Re-order gimple-fold.h include.

gcc/
	* gimple-fold.cc (gimple_build): Adjust for new
	main API.
	* gimple-fold.h (gimple_build): New main APIs with
	iterator, insert direction and iterator update.
	(gimple_build): New forwarder template.
	(clear_padding_type_may_have_padding_p): Remove.
	(clear_type_padding_in_mask): Likewise.
	(arith_overflowed_p): Likewise.
	* fold-const.h (clear_padding_type_may_have_padding_p): Declare.
	(clear_type_padding_in_mask): Likewise.
	(arith_overflowed_p): Likewise.
	* tree-vect-generic.cc (gimplify_build3): Use main gimple_build API.
	(gimplify_build2): Likewise.
	(gimplify_build1): Likewise.
	* ubsan.cc (ubsan_expand_ptr_ifn): Likewise, avoid extra
	compare stmt.
	* gengtype.cc (open_base_files): Re-order includes.
	* builtins.cc: Re-order gimple-fold.h include.
	* calls.cc: Likewise.
	* cgraphbuild.cc: Likewise.
	* cgraphunit.cc: Likewise.
	* config/rs6000/rs6000-builtin.cc: Likewise.
	* config/rs6000/rs6000-call.cc: Likewise.
	* config/rs6000/rs6000.cc: Likewise.
	* config/s390/s390.cc: Likewise.
	* expr.cc: Likewise.
	* fold-const.cc: Likewise.
	* function-tests.cc: Likewise.
	* gimple-match-head.cc: Likewise.
	* gimple-range-fold.cc: Likewise.
	* gimple-ssa-evrp-analyze.cc: Likewise.
	* gimple-ssa-evrp.cc: Likewise.
	* gimple-ssa-sprintf.cc: Likewise.
	* gimple-ssa-warn-access.cc: Likewise.
	* gimplify.cc: Likewise.
	* graphite-isl-ast-to-gimple.cc: Likewise.
	* ipa-cp.cc: Likewise.
	* ipa-devirt.cc: Likewise.
	* ipa-prop.cc: Likewise.
	* omp-low.cc: Likewise.
	* pointer-query.cc: Likewise.
	* range-op.cc: Likewise.
	* tree-cfg.cc: Likewise.
	* tree-if-conv.cc: Likewise.
	* tree-inline.cc: Likewise.
	* tree-object-size.cc: Likewise.
	* tree-ssa-ccp.cc: Likewise.
	* tree-ssa-dom.cc: Likewise.
	* tree-ssa-forwprop.cc: Likewise.
	* tree-ssa-ifcombine.cc: Likewise.
	* tree-ssa-loop-ivcanon.cc: Likewise.
	* tree-ssa-math-opts.cc: Likewise.
	* tree-ssa-pre.cc: Likewise.
	* tree-ssa-propagate.cc: Likewise.
	* tree-ssa-reassoc.cc: Likewise.
	* tree-ssa-sccvn.cc: Likewise.
	* tree-ssa-strlen.cc: Likewise.
	* tree-ssa.cc: Likewise.
	* value-pointer-equiv.cc: Likewise.
	* vr-values.cc: Likewise.

gcc/testsuite/
	* gcc.dg/plugin/diagnostic_group_plugin.c: Reorder or remove
	gimple-fold.h include.
	* gcc.dg/plugin/diagnostic_plugin_show_trees.c:
	Likewise.
	* gcc.dg/plugin/diagnostic_plugin_test_inlining.c:
	Likewise.
	* gcc.dg/plugin/diagnostic_plugin_test_metadata.c:
	Likewise.
	* gcc.dg/plugin/diagnostic_plugin_test_paths.c:
	Likewise.
	* gcc.dg/plugin/diagnostic_plugin_test_show_locus.c:
	Likewise.
	* gcc.dg/plugin/diagnostic_plugin_test_string_literals.c: Likewise.
	* gcc.dg/plugin/diagnostic_plugin_test_tree_expression_range.c:
	Likewise.
	* gcc.dg/plugin/finish_unit_plugin.c: Likewise.
	* gcc.dg/plugin/ggcplug.c: Likewise.
	* gcc.dg/plugin/must_tail_call_plugin.c: Likewise.
	* gcc.dg/plugin/one_time_plugin.c: Likewise.
	* gcc.dg/plugin/selfassign.c: Likewise.
	* gcc.dg/plugin/start_unit_plugin.c: Likewise.
	* g++.dg/plugin/selfassign.c: Likewise.