Updates for split into two repos and container build

Updates after split to two repos

Bump actions/cache from 2 to 3

Bumps [actions/cache](https://github.com/actions/cache) from 2 to 3.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v2...v3)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

allow CI on all branches

pin skip-duplicate-actions

use non-editable install for unlocked phasees

new skip CI approach

changes in features.rst

fix tests

fix tests

ensure requirements.txt not zero length

tidy docs

tests inside container

refactor container build

update code.yml to use container

Author: dependabot[bot]

.containerignore

@@ -0,0 +1,6 @@
+Dockerfile
+build/
+dist/
+.mypy_cache
+.tox
+.venv*

.devcontainer.json

@@ -0,0 +1,41 @@
+// For format details, see https://aka.ms/devcontainer.json
+{
+    "name": "Python 3 Developer Container",
+    "build": {
+        "dockerfile": "Dockerfile",
+        "target": "build",
+        "context": ".",
+        "args": {}
+    },
+    "remoteEnv": {
+        "DISPLAY": "${localEnv:DISPLAY}"
+    },
+    // Set *default* container specific settings.json values on container create.
+    "settings": {
+        "python.defaultInterpreterPath": "/usr/local/bin/python",
+        "python.linting.enabled": true
+    },
+    // Add the IDs of extensions you want installed when the container is created.
+    "extensions": [
+        "ms-python.python",
+        "ms-python.vscode-pylance"
+    ],
+    // Make sure the files we are mapping into the container exist on the host
+    "initializeCommand": "bash -c 'for i in $HOME/.inputrc $HOME/.bashrc_dev; do [ -f $i ] || touch $i; done'",
+    "runArgs": [
+        "--privileged",
+        "--net=host",
+        "-v=${localEnv:HOME}/.ssh:/root/.ssh",
+        "-v=${localEnv:HOME}/.bashrc_dev:/root/.bashrc",
+        "-v=${localEnv:HOME}/.inputrc:/root/.inputrc"
+    ],
+    "mounts": [
+        // map in home directory - not strictly necessary but useful
+        "source=${localEnv:HOME},target=${localEnv:HOME},type=bind,consistency=cached"
+    ],
+    // make the workspace folder the same inside and outside of the container
+    "workspaceMount": "source=${localWorkspaceFolder},target=${localWorkspaceFolder},type=bind",
+    "workspaceFolder": "${localWorkspaceFolder}",
+    // After the container is created, install the python project in editable form
+    "postCreateCommand": "pip install $([ -f requirements_dev.txt ] && echo -r requirements_dev.txt ) -e .[dev]"
+}