Fix password text boxes having distinguishable key sounds

[frenzibyte]

• Depends on Add TextBox event handlers osu-framework#3289
• Depends on Remove all audio-related logic from TextBox osu-framework#3290 (to avoid duplicate sample plays)
• Depends on framework bump

Closes ppy/osu-framework#3280

Was aware of whether to create a dictionary holding all samples inside Keyboard resources folder (by some LINQ-ing and string manipulation) or store each sample in its own field, but chose the latter for simplicity.