fix: button uses text align and button container uses flex props

[ctoddy]

Description

Button was updated to use textAlign and other supporting props (contain) and buttonContainer strictly uses flex props since textAlign does not work with flex props. Key's now use flex props only.

see LUI-1503

Changes

• textAlign property removed from Button Container & Key but kept for Button
• Button Container uses flex props
• flex props arg removed from Button story

Testing

• Start local
• Go to button, observe text is centered
• Go to button container, observe text and icon is centered
• Go to key, observe text is centered

[anthony9187]

noticing some weird behavior

button + flexStart

button + flexEnd

it may actually be the case that textAlign is better for buttons, or we may need to be a little more creative on how we handle justifying the content

[ctoddy]

@anthony9187 wanted to confirm, we wanted to keep alignItems for the button strictly center? or was this expected to be a prop users can control with a supporting arg for the Button story?