Part of #123569

This patch pushes the error handling boundary for the GetBitSize()
methods from Runtime into the Type and CompilerType APIs. This makes it
easier to diagnose problems thanks to more meaningful error messages
being available. GetBitSize() is often the first thing LLDB asks about a
type, so this method is particularly important for a better user
experience.

rdar://145667239

As part of the "RemoveDIs" work to eliminate debug intrinsics, we're
replacing methods that use Instruction*'s as positions with iterators. A
number of these (such as getFirstNonPHIOrDbg) are sufficiently
infrequently used that we can just replace the pointer-returning version
with an iterator-returning version, hopefully without much/any
disruption.

Thus this patch has getFirstNonPHIOrDbg and
getFirstNonPHIOrDbgOrLifetime return an iterator, and updates all
call-sites. There are no concerns about the iterators returned being
converted to Instruction*'s and losing the debug-info bit: because the
methods skip debug intrinsics, the iterator head bit is always false
anyway.

InsertPosition has been deprecated in favor of using
BasicBlock::iterator. (See #102608)

As specified in the docs,
1) raw_string_ostream is always unbuffered and
2) the underlying buffer may be used directly

( 65b13610a5226b84889b923bae884ba395ad084d for further reference )

* Don't call raw_string_ostream::flush(), which is essentially a no-op.
* Avoid unneeded calls to raw_string_ostream::str(), to avoid excess
indirection.

The constructor initializes `*this` with a copy of `M->getDataLayout()`,
which can just be spelled as `DataLayout DL = M->getDataLayout()`. In
all places where the constructor is used, Module outlives DataLayout, so
store a reference to it instead of cloning.

Pull Request: https://github.com/llvm/llvm-project/pull/102839

Note that StringRef::equals has been deprecated in favor of
operator==(StringRef, StringRef).

This patch replaces uses of StringRef::{starts,ends}with with
StringRef::{starts,ends}_with for consistency with
std::{string,string_view}::{starts,ends}_with in C++20.

I'm planning to deprecate and eventually remove
StringRef::{starts,ends}with.

These have been removed in 7b9d73c2f90c0ed8497339a16fc39785349d9610.
This is a followup patch to apply the changes to lldb.

The corresponding definitions were removed in 7dcbe3d3 and 2a8fa2a8.
Also remove a couple of variables made dead by those changes.