[RFC]: add missing double precision `nan` modules for `stats/strided`

### Description

This RFC proposes to add missing double precision `nan` modules for `stats/strided`, which include :
- [ ] dnanmeankbn
- [ ] dnanmeankbn2
- [ ] dnanmeanli
- [ ] dnanmeanlipw
- [ ] dnanmeanstdev
- [ ] dnanmeanstdevpn
- [ ] dnanmeanvar
- [ ] dnanmeanvarpn
- [ ] dsnanmeanpw
- [ ] dsnanvariance
- [ ] dsnanvariancepn
- [ ] dsnanstdev
- [ ] dsnanstdevpn
- [ ] dsnanmeankbn
- [ ] dsnanmeankbn2
- [ ] dsnanmeanli
- [ ] dsnanmeanlipw
- [ ] dnansem
- [ ] dnansemch
- [ ] dnansempn
- [ ] dnansemtk
- [ ] dnansemwd
- [ ] dnansemyc
- [ ] dnanmidrangeabs
- [ ] dnancumax
- [ ] dnancumaxabs
- [ ] dnancumin
- [ ] dnancuminabs

NOTE: Priority is top to bottom.

### Related Issues

None

### Questions

- How many packages do we really need ? ( I have already eliminate those packages which not useful or not feasible )
- What should be the priority of all the modules mentioned here?

### Other

No.

### Checklist

- [x] I have read and understood the [Code of Conduct](https://github.com/stdlib-js/stdlib/blob/develop/CODE_OF_CONDUCT.md).
- [x] Searched for existing issues and pull requests.
- [x] The issue name begins with `RFC:`.

The issue identifies stats/strided as the entry point and lists the proposed double-precision NaN modules in priority order. Start by reviewing existing modules in that area, then resolve the package-count and priority questions; done means the agreed modules are added consistently.

Vom Indexierungsmodell aus dem Issue-Text verfasst.