Auto merge of #108717 - TDecki:dec2flt-inline, r=thomcc

Add inlining annotations in `dec2flt`.

Currently, the combination of `dec2flt` being generic and the `FromStr` implementaions
containing inline anttributes causes massive amounts of assembly to be generated whenever
these implementation are used. In addition, the assembly has calls to function which ought to
be inlined, but they are not (even when using lto).

This Pr fixes this.

Author: bors