gitlab-ci: enable auto skip pending jobs/pipelines

Needed to enable ability to skip running/pending jobs/pipelines in
running gitlab-ci queue on developers branches. As found this feature
had 2 special switching check boxes in gitlab-ci CI/CD configuration:
  https://gitlab.com/help/ci/pipelines/settings#auto-cancel-pending-pipelines

To make it workable the whole testing project in gitlab-ci must be
either with these options or w/o it. But in the same project there are
release branches testing, which must be run for each push and can't be
skipped. To resolve this issue found the single solution to split
gitlab-ci project in two:
  new one with testing on branches which can be skipped:
    https://gitlab.com/tarantool/tarantool-core-branches/
  and old one on branches that can't be skipped:
    https://gitlab.com/tarantool/tarantool/

Current patch can be pushed into release branches only after the new
gitlab-ci project https://gitlab.com/tarantool/tarantool-core-branches/
will be completely prepared as https://gitlab.com/tarantool/tarantool/.

Closes #5035

.branches.gitlab-ci.yml

@@ -0,0 +1,161 @@
+stages:
+  - test
+  - perf
+  - cleanup
+
+variables:
+  PACK_RULE: package
+
+.develope_only_template:
+  only:
+    - branches
+    - schedules
+    - external_pull_requests
+    - merge_requests
+
+.full_only_template:
+  only:
+    - /^.*-full-ci$/
+    - schedules
+    - external_pull_requests
+    - merge_requests
+
+.pack_only_template:
+  extends: .full_only_template
+
+.perf_only_template:
+  only:
+    - /^.*-full-ci-perf$/
+    - /^.*-perf$/
+    - external_pull_requests
+    - merge_requests
+  except:
+    - schedules
+
+# Jobs templates
+
+include:
+  - '.templates.gitlab-ci.yml'
+  - '.perf.gitlab-ci.yml'
+
+# Tests release and debug
+
+release:
+  extends:
+    - .develope_only_template
+    - .test_release_template
+
+debug:
+  extends:
+    - .develope_only_template
+    - .test_debug_template
+
+# Clang builds (Clang/Clang+LTO/Clang8+LTO/Clang8+ASAN)
+
+release_clang:
+  extends:
+    - .develope_only_template
+    - .test_release_clang_template
+
+release_lto:
+  extends:
+    - .full_only_template
+    - .test_release_lto_template
+
+release_lto_clang8:
+  extends:
+    - .full_only_template
+    - .test_release_lto_clang8_template
+
+release_asan_clang8:
+  extends:
+    - .develope_only_template
+    - .test_release_asan_clang8_template
+
+# Static builds w/ & w/o dockerfile
+
+static_build:
+  extends:
+    - .develope_only_template
+    - .test_static_build_template
+
+static_docker_build:
+  extends:
+    - .full_only_template
+    - .test_static_docker_build_template
+
+# OSX builds (14/15/15+LTO)
+
+osx_14_release:
+  extends:
+    - .full_only_template
+    - .test_osx_14_release_template
+
+osx_15_release:
+  extends:
+    - .develope_only_template
+    - .test_osx_15_release_template
+
+osx_15_release_lto:
+  extends:
+    - .full_only_template
+    - .test_osx_15_release_lto_template
+
+# FreeBSD build
+
+freebsd_12_release:
+  extends:
+    - .develope_only_template
+    - .test_freebsd_12_release_template
+
+# Build only packages and sources
+
+sources:
+  extends: .pack_template
+  script:
+    - ${GITLAB_MAKE} source
+
+centos_6:
+  extends: .test_centos_6_template
+
+centos_7:
+  extends: .test_centos_7_template
+
+centos_8:
+  extends: .test_centos_8_template
+
+fedora_28:
+  extends: .test_fedora_28_template
+
+fedora_29:
+  extends: .test_fedora_29_template
+
+fedora_30:
+  extends: .test_fedora_30_template
+
+fedora_31:
+  extends: .test_fedora_31_template
+
+ubuntu_14_04:
+  extends: .test_ubuntu_14_04_template
+
+ubuntu_16_04:
+  extends: .test_ubuntu_16_04_template
+
+ubuntu_18_04:
+  extends: .test_ubuntu_18_04_template
+
+ubuntu_19_10:
+  extends: .test_ubuntu_19_10_template
+
+ubuntu_20_04:
+  extends: .test_ubuntu_20_04_template
+
+debian_8:
+  extends: .test_debian_8_template
+
+debian_9:
+  extends: .test_debian_9_template
+
+debian_10:
+  extends: .test_debian_10_template