Make allow text and icon overlap true by default

[tobrun]

Having the default value false, has led to confusion for our end users. The default value of false makes sense for symbols used in the style as labels and icons but for end-user added symbols, which are always important, we should not hide them by default. This is a breaking change and requires a semver major update.

          symbolManager.setIconAllowOverlap(true);
          symbolManager.setTextAllowOverlap(true);