Hide nonce implementation details in metadata (#6562)

See https://github.com/polkadot-fellows/runtimes/issues/248 : using
`TypeWithDefault` having derived `TypeInfo` for `Nonce` causes a
breaking change in metadata for nonce type because it's no longer `u64`.

Adding a default implementation of `TypeInfo` for `TypeWithDefault` to
restore the original type info in metadata.

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Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>