qapi: Use 'struct' instead of 'type' in schema

Referring to "type" as both a meta-type (built-in, enum, union,
alternate, or struct) and a specific type (the name that the
schema uses for declaring structs) is confusing. Do the bulk of
the conversion to "struct" in qapi schema, with a fairly
mechanical:

for f in `find -name '*.json'; do sed -i "s/'type'/'struct'/"; done

followed by manually filtering out the places where we have a
'type' embedded in 'data'. Then tweak a couple of tests whose
output changes slightly due to longer lines.

I also verified that the generated files for QMP and QGA (such
as qmp-commands.h) are the same before and after, as assurance
that I didn't leave in any accidental member name changes.

Backports commit 895a2a80e0e054f0d5d3715aa93d10d15e49f9f7 from qemu

qemu/qapi-schema.json

@@ -31,7 +31,7 @@
 #
 # Since: 1.5
 ##
-{ 'type': 'X86CPUFeatureWordInfo',
+{ 'struct': 'X86CPUFeatureWordInfo',
   'data': { 'cpuid-input-eax': 'int',
             '*cpuid-input-ecx': 'int',
             'cpuid-register': 'X86CPURegister32',