MDL-45371 behat: Tests for block glossary_random
MDL-45294 behat: Supporting an aria-label as a block ref
MDL-45294 behat: Updating block references to aria label value

Also improving moodle selectors xpath expressions
readability.
MDL-45320 behat: Step definitions for blocks
MDL-45320 block_html: behat tests
MDL-45320 behat: change to block selector
Merge branch 'wip-MDL-45371-m26' of git://github.com/marinaglancy/moodle into MOODLE_26_STABLE