Improve formatting for various types

[cmpute]

• For UBig / IBig
  • Implement {:x?} and {:X?} formatting (Wait until the format flags are exposed through public API)
• For FBig
  • Implement {:x} and {:X} formatting for base 2. It should print the float as something like 0xabcp-n.
  • Implement {:e} and {:E} formatting. It should prints 999e-n for base 10, and xxx@-yy for other bases.
• For RBig / Relaxed
  • Implement Debug
  • Implement {:b}, {:x}, {:X} by printing the components separately
  • Implement .in_radix() by printing the components separately
  • Implement .in_expanded() by printing the decimal form, which prints to certain digits after the radix point by default. It will support {:e}, {:E} as well. It should also supports printing the repeatant with the alternative flag set. Might also support other radices as well.

    format!("{}", rbig!(1/3).in_expanded(10)) -> 1.3333333 (maybe depends on the word size)
    format!("{:.4}", rbig!(1/3).in_expanded(10)) -> 1.3333
    format!("{:#.4}", rbig!(1/3).in_expanded(10)) -> 1.(3)
    format!("{:e}", rbig!(1/3).in_expanded(10)) -> 1.3e0
    format!("{:.4e}", rbig!(1/3).in_expanded(10)) -> 1.3333e0
    

(See here for repeatant detection implementation example)