Use `llvm::Error` instead of `CommandReturnObject` for error reporting.
The command return objects were populated with errors but never
displayed. With this patch they're at least logged.

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.

[lldb] Part 1 of 2 - Refactor `CommandObject::Execute(...)` to return
`void` instead of ~~`bool`~~

Justifications:
- The code doesn't ultimately apply the `true`/`false` return values.
- The methods already pass around a `CommandReturnObject`, typically
with a `result` parameter.
- Each command return object already contains:
	- A more precise status
	- The error code(s) that apply to that status

Part 2 refactors the `CommandObject::DoExecute(...)` method.
- See
[https://github.com/llvm/llvm-project/pull/69991](https://github.com/llvm/llvm-project/pull/69991)

rdar://117378957

Fix a mutation of `CommandAlias::m_option_args_sp`, which resulted in cases where
aliases would fail to run on second, and subsequent times.

For example, an alias such as:

```
command alias p1 p 1
```

When run the second time, the following error would be reported to the user:

```
error: expression failed to parse:
error: <user expression 1>:1:1: expression is not assignable
--  1
^   ~
```

To fix this, `CommandAlias::Desugar` now constructs options to a freshly constructed
vector, rather than by appending to the results of `GetOptionArguments`.

rdar://107770836

Differential Revision: https://reviews.llvm.org/D150078

    This reverts commit ac05bc0524c66c74278b26742896a4c634c034cf.

I had incorrectly removed one set of checks in the option handling in
Options::ParseAlias because I couldn't see what it is for.  It was a
bit obscure, but it handled the case where you pass "-something=other --"
as the input_line, which caused the built-in "run" alias not to return
the right value for IsDashDashCommand, causing TestHelp.py to fail.

This reverts commit 6c089b2af5d8d98f66b27b67f70958f520820a76.

This was causing the test test_help_run_hides_options from TestHelp.py to
fail on Linux and Windows (but the test succeeds on macOS).  The decision
to print option information is determined by CommandObjectAlias::IsDashDashCommand
which was changed, but only by replacing an inline string constant with a const char *
CommandInterpreter::g_argument which has the same string value.  I can't see why this
would fail, I'll have to spin up a vm to see if I can repo there.

It didn't help.

This reverts commit 81f8788528886ee611041e1f4ee54eea8bbfa277.

Sadly, the test passes on macOS, but fails on Ubuntu & Win.  The
extra option printing is supposed to be suppressed by the return
from CommandObjectAlias::IsDashDashCommand.  That was changed, but just
by replacing an inline string compare with a const string from
CommandInterpreter.  Putting the old version back temporarily to
see if that is really the problem.

This is particularly a problem for alias construction, where you might
want to have a backtick surrounded option in the alias.  Before this
patch:

command alias expression -Z \`argc\` -- argv

for instance would be rendered as:

expression -Z argc -- argv

and would fail to work.

Differential Revision: https://reviews.llvm.org/D133045

Since https://reviews.llvm.org/D103701 AppendError<...>
sets this for you.

This change includes all of the non-command uses.

Some uses remain where it's either tricky to reason about
the logic, or they aren't paired with AppendError calls.

Reviewed By: teemperor

Differential Revision: https://reviews.llvm.org/D104379