Numerous additions & fixes

Fixes

• Update rules_nodejs to 0.42.3 (#1324)
• Update io_bazel_rules_rust commit hash to 959ba56 (#1321)
• Update dependency bazel_toolchains to v1.2.4 (#1320)
• Add digest field back to to PushInfo (#1315)
• Update dependency io_bazel_rules_go to v0.20.3 (#1313)
• Update dependency bazel_toolchains to v1.2.2 (#1312)
• Update rules_python commit hash to 38f86fb (#1311)
• Add note about go_image on Mac (#1309)
• Sync with internal change (#1308)
• Update rules_groovy to prepare for Bazel 2.0 (#1307)
• Update io_bazel_rules_scala commit hash to 886bc9c (#1306)
• Update dependency bazel_toolchains to v1.2.1 (#1304)
• Update io_bazel_rules_scala commit hash to e568402 (#1303)
• Sync with internal change (#1301)
• move python modules out of bzl file (#1299)
• Sync with internal change (#1298)
• Update dependency bazel_toolchains to v1.2.0 (#1295)
• Update io_bazel_rules_scala commit hash to ff57530 (#1294)
• Update io_bazel_rules_rust commit hash to 3251240 (#1293)
• Fix ordering of docker entrypoint and entrypoint prefix (#1291)
• Move tests that use 'docker' to GCB (#1290)
• Update rules_python commit hash to 9467740 (#1289)
• Deprecate the Kaniko tool to build images from Dockerfile (#1288)
• Update dependency bazel_toolchains to v1.1.2 (#1279)
• install_pkgs uses named volumes to work with DIND. (#1277)
• Replace merge_dicts with dicts.add (#1276)
• added support for user defined tags on generated container_import r… (#1274)
• define gzip in the docker toolchain not as a local tool (#1272)
• config_stripper no longer stores full file in RAM. (#1271)
• Update rules_python commit hash to 7b222cf (#1270)
• Update io_bazel_rules_scala commit hash to 26cf9b7 (#1269)
• Update dependency bazel_toolchains to v1.1.1 (#1268)
• Update io_bazel_rules_rust commit hash to ec436b5 (#1267)
• Dont assume docker path in image util (#1262)
• Make config stripper handle image tarballs with symlinked layers (#1261)
• Format README to sync with internal repo (#1260)
• Update dependency io_bazel_rules_go to v0.20.2 (#1259)
• Update rules_python commit hash to a610ace (#1258)
• Update io_bazel_rules_rust commit hash to b94d3a4 (#1257)
• Update rules_python commit hash to 230f6d1 (#1252)
• Fix rules_go mirror URL (#1251)
• Update README for release v0.12.1 (#1249)