Improvements needed for testing suite

The following are based on my work on enabling checkAllCommands(). Checking off the current issues will allow for tests to be written without the need of try-catch blocks.

I'm also using it as a general tracking on for other issues.

- [ ] ability to check if a creature can attack at all and a specific target.
- [ ] ability to list all available targets and to check if a specific target is valid.
- [ ] Change implementation of certain abilities and effects that disallow certain abilities and actions to NOT be used so that they can work with checkPlayableAbility. See #8960
- [ ] More documentation of the constants and functions used.
- [ ] checkPlayableAbility needs to be able to check is spells are castable when other spells are on the stack.