Rollup merge of #144613 - pantsman0:nintendo_switch_cpu_features, r=wesleywiser

aarch64-nintendo-switch-freestanding - Enable CPU features that are always available in a live system (crypto instructions, plus explicit NEON).

~~While some NEON and crypto features may not be supported on the Nintendo Switch at boot (e.g. on the a53 cores) and this has not been tested, the features will _always_ be available if running as a sysmodule or homebrew application under Horizon/Atmosphere.~~ EDIT:  the a53 cores are fused out, these features are always available.

This has been tested with local tools personally, as well as building [emuiibo](https://github.com/XorTroll/emuiibo) as it uses both `sha` and `aes` primitives. This was tested using inline assembly in previous versions, and in current versions by using the `aes`, `ctr`, `hmac`, and `sha2` crates.

r? `@jam1garner`

This ended up being much delayed from our discussions about updating this. I tested a number of individual features such as the `aes` and `sha2` target-features directly to avoid a warning message with the `crypto` feature, but that appears to be caused by rust-lang/rust#96472 and is not actually an issue.

There is also a decision to make here about explicitly enabling the `neon` feature. I am in favor of it to be explicit, but it is not necessary as it is already enabled by the `v8a` and `crypto` features. I will defer to your decision as it does not change the actual instructions available for codegen.

Author: jhpratt