Expose native input as slot for input components (Input, Select, ...)

[ChronicStone]

This function solves the problem (这个功能解决的问题)

The main issue this aims to solve is the lack of a masking feature on the text input. Developing / integrating a masking library for Naive UI implies a certain number of complications.

Exposing the native input as as lot, in addition of letting users implement by themselves the masking library of their choice, but also opens up interesting possibilities regarding input control.

Expected API (期望的 API)

Following a discussion with @07akioni, his proposal was to expose the native input through an optional slot.