Make basepoint table constants &'static references

[tarcieri]

All current accesses to the basepoint tables currently use explicit borrowing.

It's good borrowing is used to prevent them from being copied onto the stack, however instead of requiring the caller to borrow the constant, instead the constant can simply be defined as a &'static reference.

Closes #486 (I think? cc @elichai)

[elichai]

According to the rust reference: https://doc.rust-lang.org/reference/items/constant-items.html

References to the same constant are not necessarily guaranteed to refer to the same memory address.

So the reference doesn't guarantee that the current implementation won't end up duplicating the table

And I'm not longer sure that even a const reference is enough: rust-lang/rust#72004

[tarcieri]

Okay, I figured out how to make all of the basepoint tables static in d69e67c.

They're now all static as well as &'static references. Not sure if that's overkill or not.

[tarcieri]

Went ahead and squashed and split out the rustfmt changes into a separate commit.

There are <50 lines of actual changes in 59b4f6b 00df378 (rebased) but thanks to rustfmt it's over 9000 total.

[tarcieri]

Phew, green again.

Sidebar: we might consider feature-gating these basepoint tables. Embedded users would probably appreciate that. Edit: opened #489

[rozbb]

Looks good, thank you! This is how I checked the fmt step:

/t/curve25519-dalek (main)$ git diff 3c6ed86^..3c6ed86 | shasum -a 256
    42953ce3fdbb4f7297d5dfe2b1647977325047b68a8cc72b10e68adf534d4b46  -
/t/curve25519-dalek (main)$ git checkout 3c6ed86^
/t/curve25519-dalek ((00df3786…))$ cargo fmt
/t/curve25519-dalek ((00df3786…))$ git diff | shasum -a 256
    42953ce3fdbb4f7297d5dfe2b1647977325047b68a8cc72b10e68adf534d4b46  -