Simplify UUIDv7 options

[ryanwinchester]

Simplify the UUIDv7 options and make them more opinionated and easier to use.

• Too much flexibility means too easy to use in a weird way.
• There isn't really a good reason to use monotonic in combination with milliseconds.
• Nanoseconds wasn't really nanoseconds, but sub-milliseconds based on nanoseconds, stepped across 12 bits

Since there hasn't been a release yet since the UUIDv7 options were added, it's a good time to do this.

Before

Options:

• precision: :millisecond | :nanosecond
• monotonic: true | false

After

Options:

• precision: :millisecond | :monotonic

[josevalim]

Love it! 💚 💙 💜 💛 ❤️