instanceCachingFactory not cleared on clearInstances

[vitorvanacor]

Describe the bug
Calling container.clearInstances() does not clear instances created by instanceCachingFactory. If this is not a bug, but by design, what is the correct way of achieving this behaviour?

To Reproduce

import "reflect-metadata";
import {container} from "tsyringe";

function main() {
  container.register('port', {
    useFactory: instanceCachingFactory(() => process.env.PORT),
  })
  process.env.PORT = '1234'
  assert(container.resolve('port') === '1234')
  process.env.PORT = '5678'
  // Still resolves to '1234' (OK)
  assert(container.resolve('port') === '1234')
  container.clearInstances()
  // Should run factory again and resolve to '5678'
  assert(container.resolve('port') === '5678') // Error! It is still resolving to '1234'
}

main()

Expected behavior
After clearInstances, the instanceCachingFactory should run again - at least this is what I expect since it is what happens with @singleton, registerSingleton and { lifecycle: Lifecycle.Singleton } and the README says that instanceCachingFactory is very similar to singleton.
johan13 has created a good alternative here: #140 (comment)
But shouldn't this be supported by the library?

Version: 4.6.0