targets 1.12.0

• Avoid loading non-targets in tar_load(everything()) (#1529, @pitakakariki).
• For internal consistency, return NA_character_ from tar_path_target() when format is "file" (#1532, @noamross).
• Add tar_option_unset() (#1521, @noamross).
• Use a new TAR_ACTIVE environment variable instead of a field of the tar_runtime object for tar_runtime() (ropensci/tarchetypes#232, @lgaborini).
• Add tar_igraph() and recommend it along with igraph::find_cycle() for debugging (#1562, @tylermorganwall).
• Avoid the unclean shutdown message in the clustermq multi-process scheduler by calling cleanup() repeatedly until it returns TRUE. Uses exponential backoff to avoid excessive CPU load.
• Use sequential controller in covr.
• Ensure hash stability of vector slices in R >= 4.6.0 (#1566).
• Use a dummy send instead of send_wait() to work around mschubert/clustermq#340 (#1566).
• Set strict = TRUE by default in tidyselect::eval_select() to make tidyselect interfaces consistent with dplyr::select() (except the exclude argument of graph functions, which need to allow names to not exist in the list of choices) (#1563, @statzhero).