fix: improve bitmap field editor styles for large images and/or no buttons#2360

maribethb merged 2 commits intoRaspberryPiFoundation:masterRaspberryPiFoundation/blockly-samples:masterfrom

mikeharv:fix-bitmap-field-dropdown-stylesmikeharv/blockly-samples:fix-bitmap-field-dropdown-stylesCopy head branch name to clipboard