Revert "Info: Set fixed size true for pref app menu field"

This reverts commit 879020baf11d142a48ba1714fcca1c419b93a4c3.
Style fixes to BMenuField

Rename resize to resizingMode, whitespace fixes, compare to 0 explicitly
Use better variable names in SetDivider
Don't cast to float, use floorf
Remove the unused bounds parameter from DrawLabel

Also refactor BMenuField::Draw()
BMenuField: Fix menu bar resizing in auto-size mode.

Fixes #9753 (for real this time)

Don't resize the menu field when the menu bar resizes, the menu
field stays the same size because we'll need to use it's width to
check when the menu bar width has expanded beyond its width.
Then, if the selected menu item expands the menu bar to a width
greater than the width of the menu field resize it to the menu field
width.