MISC: Validate bet input of casino mini games

[catloversg]

The "bet input" of 3 games (Coin flip, Slot machine, Roulette) has many problems:

• The validation logic is duplicated.
• The validation logic does not check the current player's money.
• When the bet amount is "out-of-range", it's silently changed to the min/max value.
• When the bet amount is invalid, there is no error shown in the UI.
• There is no way to know the max bet amount of a game.

Blackjack does not have these problems, so this PR pulls the "bet input" of Blackjack out and reuses it in other games.

Before:

After:

[d0sboots]

Nice, the greater consistency looks good. This will of course mess up existing Casino scripts (again) XD

[d0sboots]

Oh no I forgot to send these pending comments from forever ago

[catloversg]

I updated based on your feedback. I also made 2 changes to make the behaviors of 4 games more consistent.
Currently, their behaviors are like this:

• All games enable the play button without checking the bet, except Blackjack.
• Roulette and slot machine call reachedLimit() after playing. Coin flip and blackjack do not.

My changes:

• All games enable the play button without checking the bet. We will check the bet after the player presses the play button.
• No game calls reachedLimit() after playing. We only need to call it after the player presses the play button.