The methods are now attached to CodegenCx instead of Type

Moved common enums to common

Prelude to using associated types in traits rather than type parameters

Generalized operand.rs#nontemporal_store and fixed tidy issues

Generalized operand.rs#nontemporal_store's implem even more
With a BuilderMethod trait implemented by Builder for LLVM

Cleaned builder.rs : no more code duplication, no more ValueTrait

Full traitification of builder.rs

Generalized FunctionCx

Added ValueTrait and first change

Generalize CondegenCx

Generalized the Builder struct defined in librustc_codegen_llvm/builder.rs

With emscripten removed in #55626, we no longer need to support
building against LLVM 4.

If LLVM 7 is used, generate memcpy/memmove with differing
src/dst alignment. I've added new FFI functions to construct
these through the builder API, which is more convenient than
dealing with differing intrinsic signatures depending on the
LLVM version.

LLVM requires that atomic loads and stores be aligned to at least the size of the type.