Detect AWS and Mac platforms, and automatically set platform

[mranst]

Description

This PR adds support for detecting AWS and Mac (#539). I also added a commit that will automatically set the platform for create and tier tests based on the current host, though this can be reverted if it causes problems. This has the convenience of not need to specify -p aws every time.

@ashiklom Is there a cylc installation on AWS? I can set it up like I did on Discover

[ashiklom]

Implementation looks good.

But we should think through what exactly we mean by a "platform" and what it means for Swell to "support" said platform.

Like, do we have anyone successfully using the GENERIC or MAC platforms? You can't actually run Swell without slurm, and getting slurm running locally on a MAC seems really difficult (or flat-out impossible?).

A useful way to think about (and implement/document) this might in terms of tiers of support. Maybe something like:

1. A platform with tier0 support can run code_tests, unit tests, and maybe individual tasks if they are precisely configured.
2. A platform with tier1 support can run the tier1 tests without modification.
3. A platform with tier2 support can successfully run tier2 tests.

[ashiklom]

I'm pretty sure Swell won't actually work with the GENERIC platform, right? If that's the case, I suggest we don't actually include it as a "supported" platform here and just let any errors in this section get thrown (which would be a noteworthy error --- we're already limiting this section to Discover hostnames).

[ashiklom]

Or would this break code_tests or other unit tests running on a generic linux machine or something? I.e., Does code_tests depend on the platform? If so, it shouldn't!

[mranst]

Code tests don't depend on platform, but one quirk of the click interface is that it executes all calls in the driver group regardless of whether the particular command that needs it is called or not. So if we raise an error if the platform was not detected, it will raise that error any time swell is called for any purpose

[ashiklom]

Ah, makes sense. Can we work around that with something like this?

@swell_driver.command()
@click.argument('suite', type=click.Choice(AllSuites.config_names()))
@click.option('-m', '--input_method', 'input_method', default='defaults',
              type=click.Choice(['defaults', 'cli']), help=input_method_help)
@click.option('-p', '--platform', 'platform', default=None,     # <--- NOTE: Default to `None`
              type=click.Choice(platforms.get_all()), help=platform_help)
@click.option('-o', '--override', 'override', default=None, help=override_help)
@click.option('-a', '--advanced', 'advanced', default=False, help=advanced_help)
@click.option('-s', '--slurm', 'slurm', default=None, help=slurm_help)
def create(
    suite: str,
    input_method: str,
    platform: str | None,
    override: Union[dict, str, None],
    advanced: bool,
    slurm: str
) -> None:
    """
    Create a new experiment

    This command creates an experiment directory based on the provided suite name and options.

    Arguments: \n
        suite (str): Name of the suite you wish to run. \n

    """

    if platform is None:
        platform = platforms.detect_platform()

    # Create the experiment directory
    create_experiment_directory(suite, input_method, platform, override, advanced, slurm)

[ashiklom]

If neither of these conditions is met, suggest raising a ValueError(f"Unknown CPU architecture: {model_name}").

[ashiklom]

Per my comment above. If we've gotten this far, I suggest we just throw an error.

raise ValueError(f"Unknown or unsupported platform: {os_name}")

[ashiklom]

Re: Cylc on AWS --- Yes, I installed cylc globally. It's in /usr/local/bin/cylc.