std.fmt.formatFloat: implement 32-bit and 64-bit ryu backends

[tiehuis]

The ryu floating point formatting algorithm was recently added to std. This implemented only the 128-bit backend, which we use to print all floating point values: #19229

We should also consider implementing the 32-bit and 64-bit backends. At minimum, the 64-bit backend is valuable as it is much faster and reduces the large need for fast 128-bit integer support to make use of the existing backend. The 32-bit backend may be more valuable for smaller code-size specifically for embedded targets.

Upstream reference can be found at: https://github.com/ulfjack/ryu
An old (but outdated) implementation can be found at: https://github.com/tiehuis/zig-ryu