dev(ci): complete refactor

Nearly completely replace the original GitHub actions workflow.
Changes:

- Move from `.sh` files in `ci/steps` to steps in the workflow.
- Move from using docker images for environment to manual setup.
- Upgrade nfpm to v2.3.1

BREAKING CHANGE: official arm64 builds no longer support CentOS 7.
If you need to use CentOS 7 on arm64, build `code-server` locally.
For docs, see the yarn/npm section in `docs/install.md`.

ci/build/nfpm.yaml

@@ -10,10 +10,16 @@ description: |
 vendor: "Coder"
 homepage: "https://github.com/cdr/code-server"
 license: "MIT"
-files:
-  ./ci/build/code-server-nfpm.sh: /usr/bin/code-server
-  ./ci/build/code-server@.service: /usr/lib/systemd/system/code-server@.service
-  # Only included for backwards compat with previous releases that shipped
-  # the user service. See #1997
-  ./ci/build/code-server-user.service: /usr/lib/systemd/user/code-server.service
-  ./release-standalone/**/*: "/usr/lib/code-server/"
+
+contents:
+  - src: ./ci/build/code-server-nfpm.sh
+    dst: /usr/bin/code-server
+
+  - src: ./ci/build/code-server@.service
+    dst: /usr/lib/systemd/system/code-server@.service
+
+  - src: ./ci/build/code-server-user.service
+    dst: /usr/lib/systemd/user/code-server.service
+
+  - src: ./release-standalone/*
+    dst: /usr/lib/code-server/