Android-components: Let's get rid of ThreadUtils

[pocmo]

Most of the things in ThreadUtils shouldn't be needed anymore.

Let's:

• Deprecate it.
• Remove everything that can be done better with Coroutines
• If anything is left over: Do we still need that and if yes could it be replaced with something that works with Coroutines?

[NotWoods]

Some notes of what can be done better with coroutines:

assertOnUiThread

As far as I know, no Kotlin shortcut for this.

postToBackgroundThread

- postToBackgroundThread {
+ withContext(Dispatchers.IO) {
    // blocking code
  }

• withContext
• Dispatchers.IO

postToMainThread

- postToMainThread(Runnable {
+ withContext(Dispatchers.Main) {
    // UI thread code
- })
+ }

• withContext
• Dispatchers.Main

postToMainThreadDelayed

- postToMainThreadDelayed(Runnable {
+ delay(delayInMs)
+ withContext(Dispatchers.Main) {
    // UI thread code
- }, delayInMs)
+ }

• withContext
• delay
• Dispatchers.Main

setHandlerForTest

kotlinx-coroutines-test offers testing tools for coroutines.