Constructing Target triple with `ObjectFile::makeTriple` instead of just
with `Arch` and leaving the rest unknown. Also creating the subtarget
with the `CPU`. AMDGPU needs the full triple and `CPU` to disassemble
correctly.

To run a full test, also fixed a failure in `SIPreAllocateWWMRegs` with
the `$noreg` operand in `DBG_VALUE`.

---------

Co-authored-by: Matt Arsenault <arsenm2@gmail.com>

Identified with misc-include-cleaner.

startswith/endswith wrap starts_with/ends_with and will eventually go away (to more closely match string_view)

Note that llvm::support::endianness has been renamed to
llvm::endianness while becoming an enum class as opposed to an
enum. This patch replaces support::{big,little,native} with
llvm::endianness::{big,little,native}.

Note that llvm::support::endianness has been renamed to
llvm::endianness while becoming an enum class as opposed to an enum.
This patch replaces llvm::support::{big,little,native} with
llvm::endianness::{big,little,native}.

Update DWARFExpression::Operation and LVOperation to support more than
2 operands.

Take the opportunity to use a SmallVector, which will handle at least 2
operands without allocation anyway, and removes the static limit
completely.

As there is no longer the concept of an "unused operand", remove
Operation::Encoding::SizeNA. Any use of it is now replaced with explicit
checks for how many operands an operation has.

There are still places where the limit remains 2, namely in the
DWARFLinker and in DIExpressions, but these can be updated in later
patches as-needed.

There are no explicit tests as this is nearly NFC: no new operation is
added which makes use of the additional operand capacity yet. A future
patch adding a new DWARF extension point will include operations which
require the support.

Reviewed By: Orlando, CarlosAlbertoEnciso

Differential Revision: https://reviews.llvm.org/D147270