These are all notices which I encountered while running simpletest-D6 (https://github.com/rmuit/simpletest) on PHP7.4 / PHP8.0. Regular (non-Pressflow) Drupal will never see them because drupal_error_handler() ignores PHP Notice / Deprecated messages. Eek.

But I figured I'd scoop them up into 1 PR for those interested.

None of these fixes cover up bugs; every notice happens in cases where the 'input' value is legit.

Most of them are simple one-line fixes, except:

• The fix to _drupal_build_css_path() which I found in https://www.drupal.org/project/drupal/issues/3084953 makes the code look strange / doesn't explain what is going on, so I changed it and added PHPDoc. (_drupal_build_css_path() is a preg_replace callback.)
• I suspect db_result() was never meant to be called inside of a foreach loop, because: see the comments I made (and the code). So arguably the callers are 'buggy.' However there are so many 'buggy' callers that I opted to fix and comment db_result() instead. (Core block.module does it, but also I found the following modules on my own file system doing it: boost, comment_revisions, ibiblio, imagecache, masquerade, path_redirect, pathauto, salesforce, sf_webform, simpletest, twitter, ubercart, views_bulk_operations, weblinks, xmlsitemap.)