feat(endpoint): expose static endpoint param instructions provider

[kuhe]

This exposes the static instructions object for each command so that it can be used by other internal packages like s3 presigner and lib-upload that need to resolve the v2 endpoint of e.g. PutObjectCommand without necessarily sending an instance of that command.

before:

public resolveMiddleware() {
    this.middlewareStack.use(getEndpointPlugin(configuration, { /* instructions literal object */ })  
}

after:

public static instructions(): EndpointParameterInstructions {
    return { /* instructions literal object */ };
}

public resolveMiddleware() {
    this.middlewareStack.use(getEndpointPlugin(configuration, Command.instructions())  
}

Since the instructions are not tied to individual Command instances, the function can be static.