Rename graviton products with ARM uarch name

[alalazo]

fixes #41

Modifications:

• Change the name of the Graviton products to corresponding generic ARM uarch names
• Add generic levels for the ARM architectures
• Rename test files accordingly

[alalazo]

The versions for both arm and apple-clang need to be checked, but I guess we can do that in a follow up PR. The versions for gcc and clang should be correct, but maybe stricter than necessary - they can also be refined later.

[boegel]

Why drop the -march part?

[alalazo]

Because of this https://community.arm.com/arm-community-blogs/b/tools-software-ides-blog/posts/compiler-flags-across-architectures-march-mtune-and-mcpu

[boegel]

Maybe it's worth adding that link somewhere, maybe in the README file in this repo?

[alalazo]

Sure, we might start another doc related PR and add more generally a section on "resources" to look at when adding a new compiler.

[tgamblin]

This LGTM. We likely need to add aliases either on the spack side or within archspec python, so that the binaries continue to work.

[alalazo]

@boegel Can you re-review? Is there something missing?

[boegel]

No strong objections for my side.
This will obviously impact projects which are currently assuming that archspec will produce values like graviton2 rather than neoverse_n1, so we should make it very clear in the release notes for the next archspec release that includes these changes...