feat(ui): Improve QInput and QFile nativeEl types (fix #15128)

[yusufkandemir]

What kind of change does this PR introduce?

• Feature

Does this PR introduce a breaking change?

• No

The PR fulfills these requirements:

• It's submitted to the dev branch (or v[X] branch)

Other information:
Resolves #15128

Ships two new types: QFileNativeElement and QInputNativeElement

QInputNativeElement accepts a generic parameter:

QInputNativeElement                      // HTMLInputElement | HTMLTextAreaElement
QInputNativeElement<"textarea">          // HTMLTextAreaElement
QInputNativeElement<"text">              // Omit<HTMLInputElement, "type"> & { type: "text" }
QInputNativeElement<"text" | "number">   // Omit<HTMLInputElement, "type"> & { type: "text" | "number" }
QInputNativeElement<"text" | "textarea"> // (Omit<HTMLInputElement, "type"> & { type: "text" }) | HTMLTextAreaElement

We can't make use of the generic param for QInput.nativeEl because we don't have generic component types yet(not fully complete in Vue in a straightforward either). But, users can use this type for advanced/flexible use cases by casting their types, typing their helper functions parameters, etc. Also, further narrowing is possible by checking against the type prop:

const inputRef = ref() as Ref<QInput>;
// ...
const { nativeEl } = inputRef.value
if (nativeEl.type === 'textarea') {
  nativeEl // HTMLTextAreaElement
} else if (nativeEl.type === 'files') {
  nativeEl.files // FileList
} else {
  nativeEl.files // null
}

[rstoenescu]

Nice!