Accept a Float value in BigDecimal#div when a precision is given

[mrkn]

See https://bugs.ruby-lang.org/issues/8826

irb(main):021:0> BigDecimal(5).div(5.1)
=> 0
irb(main):022:0> BigDecimal(5).div(5.1, 8)
(irb):22:in `div': can't omit precision for a Float. (ArgumentError)
        from (irb):22:in `<main>'
        from /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/irb-1.3.8.pre.9/exe/irb:11:in `<top (required)>'
        from /home/mrkn/.rbenv/versions/3.0/bin/irb:23:in `load'
        from /home/mrkn/.rbenv/versions/3.0/bin/irb:23:in `<main>'

It is good that the second case works well.

[mrkn]

irb(main):001:0> BigDecimal(5).div(5.1.to_d, 8)
=> 0.98039216e0
irb(main):002:0> BigDecimal(5).div(BigDecimal(5.1, 8))
=> 0
irb(main):003:0> BigDecimal(5).div(BigDecimal(5.1, 8), 8)
=> 0.98039216e0

The last case may be the appropriate behavior of BigDecimal(5).div(5.1, 8).

[mrkn]

The remaining problem is the case that the precision is larger than Float::DIG+1.

irb(main):001:0> BigDecimal(5).div(5.1)
=> 0
irb(main):002:0> BigDecimal(5).div(5.1, 8)
=> 0.98039216e
irb(main):003:0> BigDecimal(5).div(5.1, Float::DIG+1)
=> 0.9803921568627451e0
irb(main):004:0> BigDecimal(5).div(5.1, Float::DIG+2)
(irb):3:in `div': precision too large. (ArgumentError)
        from (irb):3:in `<main>'
        from /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/irb-1.3.8.pre.9/exe/irb:11:in `<top (required)>'
        from /home/mrkn/.rbenv/versions/3.0/bin/irb:23:in `load'
        from /home/mrkn/.rbenv/versions/3.0/bin/irb:23:in `<main>'