Introduce `ConstUint` to make dependent types in `DefaultConfig` more adaptable (#6425)

# Description

Resolves #6193

This PR introduces `ConstUint` as a replacement for existing constant
getter types like `ConstU8`, `ConstU16`, etc., providing a more flexible
and unified approach.

## Integration

This update is backward compatible, so developers can choose to adopt
`ConstUint` in new implementations or continue using the existing types
as needed.

## Review Notes

`ConstUint` is a convenient alternative to `ConstU8`, `ConstU16`, and
similar types, particularly useful for configuring `DefaultConfig` in
pallets. It enables configuring the underlying integer for a specific
type without the need to update all dependent types, offering enhanced
flexibility in type management.

# Checklist

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"Description" and its two subsections above.
* [ ] My PR follows the [labeling requirements](

https://github.com/paritytech/polkadot-sdk/blob/master/docs/contributor/CONTRIBUTING.md#Process
) of this project (at minimum one label for `T` required)
* External contributors: ask maintainers to put the right label on your
PR.
* [ ] I have made corresponding changes to the documentation (if
applicable)
* [ ] I have added tests that prove my fix is effective or that my
feature works (if applicable)