Clean up Key types

[Egge21M]

We have quite a lot of types dealing with a mint's keysets. However the type's names are ambiguous. We should clean these up or move them into their own class.

Example: Here we have the MintKeys type describing a key set with all its key-pairs. Then we have MintKeyset which represents the a single keyset entry without the keys. MintActiveKeys is an Array of MintKeys, but MintAllKeysets is an Array of MintKeysets.

Proposed solution: Merge all these types into a single Keyset Class or type.

export type Keys = { [amount: number]: string };

export type MintActiveKeys = {
	keysets: Array<MintKeys>;
};

export type MintAllKeysets = {
	keysets: Array<MintKeyset>;
};

export type MintKeys = {
	id: string;
	unit: string;
	keys: Keys;
};

export type MintKeyset = {
	id: string;
	unit: string;
	active: boolean;
	input_fee_ppk?: number;
};