Fix floating point number representation

[jeparlefrancais]

Closes #248

This PR change the inner representation of the decimal numbers to avoid miss-formatting the numbers when printing them back.

I decided to remove the DecimalNumber::get_raw_float method from the public API.

• add entry to the changelog

[github-actions]

Coverage after merging fix-float-representation into main will be

86.69%

Coverage Report for Changed Files

File	Stmts	Branches	Funcs	Lines	Uncovered Lines
src/generator
dense.rs	88.63%	100%	93.33%	88.19%	1002–1008, 1022–1024, 1042–1046, 1054, 1063–1064, 1069, 1075, 1084–1092, 1109, 1131, 1144–1147, 1151–1154, 159–160, 162, 176–177, 179, 253–265, 267–273, 275–276, 287–289, 368, 417, 50, 507, 51–55, 57–59, 61, 614–616, 62–63, 65–68, 685, 69, 704, 80, 887, 932, 949, 976–983
mod.rs	98.65%	100%	100%	98.55%	354, 370, 374
utils.rs	94.44%	100%	96.55%	94.22%	137, 31–33, 339, 35, 353–354, 37, 370–373, 61, 71, 81
src/nodes/expressions
mod.rs	78.76%	100%	78.38%	78.85%	137–139, 143–145, 149–151, 155–157, 161–163, 167–169, 185–187, 191–193, 269, 323, 92–97
number.rs	90.62%	100%	90.54%	90.63%	205–209, 211, 221–225, 227–228, 280–284, 286, 317, 320–325, 327, 380
string.rs	95.73%	100%	92.11%	96.43%	48, 50, 93–95