Introduce a structure for lambda parameters

[konnov]

Currently, lambda definitions have their parameters as strings:

quint/quint/src/quintIr.ts

Lines 121 to 130 in 7c29089

	export interface QuintLambda extends WithId {
	/** Expressions kind ('lambda' -- operator abstraction) */
	kind: 'lambda',
	/** Identifiers for the formal parameters */
	params: string[],
	/** The qualifier for the defined operator */
	qualifier: OpQualifier,
	/** The definition body */
	expr: QuintEx,
	}

Since the operator definitions are represented with lambdas, there is no good way to refer exactly to the place where the parameter has been defined (except for giving the definition's name and the parameter name). As we discussed with @bugarela and @shonfeder, it would be good to introduce a structure for parameters, e.g.:

export interface QuintParamDef extends WithId {
  /** Expressions kind ('param' -- an operator parameter) */
  kind: 'param',
  /** The parameter name */
  name: string,
}

This would enable easier goto definition and simplify code in REPL.