[IR] Switch everything to use memory attribute

This switches everything to use the memory attribute proposed in
https://discourse.llvm.org/t/rfc-unify-memory-effect-attributes/65579.
The old argmemonly, inaccessiblememonly and inaccessiblemem_or_argmemonly
attributes are dropped. The readnone, readonly and writeonly attributes
are restricted to parameters only.

The old attributes are auto-upgraded both in bitcode and IR.
The bitcode upgrade is a policy requirement that has to be retained
indefinitely. The IR upgrade is mainly there so it's not necessary
to update all tests using memory attributes in this patch, which
is already large enough. We could drop that part after migrating
tests, or retain it longer term, to make it easier to import IR
from older LLVM versions.

High-level Function/CallBase APIs like doesNotAccessMemory() or
setDoesNotAccessMemory() are mapped transparently to the memory
attribute. Code that directly manipulates attributes (e.g. via
AttributeList) on the other hand needs to switch to working with
the memory attribute instead.

Differential Revision: https://reviews.llvm.org/D135780

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -620,8 +620,6 @@ static uint64_t getAttrKindEncoding(Attribute::AttrKind Kind) {
     return bitc::ATTR_KIND_ALLOC_SIZE;
   case Attribute::AlwaysInline:
     return bitc::ATTR_KIND_ALWAYS_INLINE;
-  case Attribute::ArgMemOnly:
-    return bitc::ATTR_KIND_ARGMEMONLY;
   case Attribute::Builtin:
     return bitc::ATTR_KIND_BUILTIN;
   case Attribute::ByVal:
@@ -640,10 +638,6 @@ static uint64_t getAttrKindEncoding(Attribute::AttrKind Kind) {
     return bitc::ATTR_KIND_HOT;
   case Attribute::ElementType:
     return bitc::ATTR_KIND_ELEMENTTYPE;
-  case Attribute::InaccessibleMemOnly:
-    return bitc::ATTR_KIND_INACCESSIBLEMEM_ONLY;
-  case Attribute::InaccessibleMemOrArgMemOnly:
-    return bitc::ATTR_KIND_INACCESSIBLEMEM_OR_ARGMEMONLY;
   case Attribute::InlineHint:
     return bitc::ATTR_KIND_INLINE_HINT;
   case Attribute::InReg: