doc: Update HACKING.md and RELEASE_CHECKLIST.md. * HACKING.md: Change documentation about updating NEWS.VERSION+1.md file. * RELEASE_CHECKLIST.md: Wrap most long lines to 80 characters. Add section on updating stable and default branch version numbers. Add pointers in "GUI translation files" to "README.md" in libgui/languages/build_ts. Update instructions for compiling with address sanitizer. Add more details to "Create new release candidate". Add more steps to "Final Release". Add names of mailings lists to "Announce final release". Remove first two steps from "Post-Release" actions.