[DOC-603] Simplify Toolchain Configuration handling

[dandimeo]

Description

This PR aims at simplifying the toolchain configuration process

• Remove $ARANGODB_BRANCH_* and $ARANGODB_SRC_ environment variables
• No need to update any file in toolchain/docker to add a new version
• lighter docker-compose file without that super long environments section

The new toolchain config.yml will now only need

generators: {generators}
 servers:
    {docs-version}: {branch}

example

generators: examples metrics error-codes
 servers:
    "3.11": "arangodb/enterprise-preview:3.11-nightly"

Upstream PRs

• 3.10: arangodb/enterprise-preview:3.10-nightly
• 3.11: arangodb/enterprise-preview:3.11-nightly
• 3.12: arangodb/enterprise-preview:devel-nightly

[arangodb-docs-automation]

Deploy Preview Available Via
https://deploy-preview-298--docs-hugo.netlify.app

[dandimeo]

/generate

[dandimeo]

• Succesfull examples generate run with new config
  https://app.circleci.com/pipelines/github/arangodb/docs-hugo/2785/workflows/612935d4-4807-410f-8574-962d7629c7ba
• Succesfull all generators generate run with new config
  https://app.circleci.com/pipelines/github/arangodb/docs-hugo/2803/workflows/3c240af7-ba16-4688-82e2-56fed27b1b9e/jobs/7222

[Simran-B]

With the env var ARANGODB_SRC set to /C/ArangoDB/arangodb and the following Docker config:

generators: examples metrics error-codes optimizer options oasisctl
servers:
  "3.12": arangodb/enterprise-preview:devel-nightly

the toolchain seems to get stuck when I run docker compose up --abort-on-container-exit:

time="2023-10-25T12:15:45+02:00" level=warning msg="The \"OVERRIDE\" variable is not set. Defaulting to a blank string."
[+] Running 1/0
 ✔ Container toolchain  Created                                                                                                                                                                                                                                          0.0s
Attaching to toolchain
toolchain  | [INIT] Toolchain setup
toolchain  | [TOOLCHAIN] Expanded Config file:
toolchain  | generators: examples metrics error-codes optimizer options oasisctl
toolchain  | servers:
toolchain  |   "3.12": arangodb/enterprise-preview:devel-nightly
toolchain  |
toolchain  | [TOOLCHAIN] Clean arangoproxy config file
toolchain  | [INIT] Setup Finished
toolchain  | [TOOLCHAIN] Starting toolchain
toolchain  | [TOOLCHAIN] Generators: examples metrics error-codes optimizer options oasisctl
toolchain  | [] [clean_docker_environment] setup docs_net docker network
toolchain  | [] [clean_docker_environment] setup arangosh and arangodb docker volume
toolchain  | arangosh
toolchain  | [] [clean_docker_environment] Cleanup orphan containers
toolchain  | "docker stop" requires at least 1 argument.
toolchain  | See 'docker stop --help'.
toolchain  |
toolchain  | Usage:  docker stop [OPTIONS] CONTAINER [CONTAINER...]
toolchain  |
toolchain  | Stop one or more running containers
toolchain  | "docker rm" requires at least 1 argument.
toolchain  | See 'docker rm --help'.
toolchain  |
toolchain  | Usage:  docker rm [OPTIONS] CONTAINER [CONTAINER...]
toolchain  |
toolchain  | Remove one or more containers
toolchain  | arangodb/enterprise-preview:devel-nightly 3.12

(hangs here for minutes with no progress)