(tracer): define more specific types for decorators

[dreamorosi]

Description of the feature request

As discussed internally, we need to define more specific types for the method decorator that currently uses the any type:

// TODO: Revisit type below & make it more specific
// eslint-disable-next-line  @typescript-eslint/no-explicit-any
type MethodDecorator = (target: any, propertyKey: string | symbol, descriptor: TypedPropertyDescriptor<any>) => any;

Related issues, RFCs

#107