Enhancement `spfx project upgrade`: Upgrade SPFx fast serve helper to v1.15

When an SPFx 1.15 project makes use of SPFx Fast Serve. Give the suggesting to upgrade the package helper to v1.15.

For version compatibility, checkout [this matrix](https://github.com/s-KaiNet/spfx-fast-serve/blob/master/docs/VersionMatrix.md).
Similar issue #3154 