feat: add assert.Consistently

[jfmyers9]

Summary

This changeset adds the assert.Consistently and it's associated functions to assert that a condition is true over the entire period of waitFor. This is useful when testing the behavior of asynchronous functions.

Changes

• assert.Consistently checks that a provided function is true for the entirety of waitFor
• assert.Consistentlyf checks that a provided function is true for the entirety of waitFor and allows for formatting the error message
• assert.ConsistentlyWithT checks that a provided function that accepts a testing.T is true for the entirety of waitFor
• assert.ConsistentlyWithTf checks that a provided function that accepts a testing.T is true for the entirety of waitFor and allows for formatting the error message

Motivation

See: https://github.com/stretchr/testify/issues/1087#issuecomment-2139222285

Related issues

Closes https://github.com/stretchr/testify/issues/1087