Consistently quote values in the docker-compose configurations

[ankon]

This commit aligns the quoting style to always use single quotes rather than an mix
of double quotes, single quotes, and no quotes.

The "no quotes" also introduced a rather ugly other problem: at least podman-compose locally
gets confused by environment variables like KAFKA_BROKER_ID: 0, and basically drops these
out, probably because '0' is a falsy value in YAML. This leads to Kafka starting up without
a broker id, and thereby it generates one for itself -- which the tests then are very unhappy about:

 FAIL  src/cluster/__tests__/brokerPool.spec.js
  ● Cluster > BrokerPool › #refreshMetadata › updates the list of brokers

    expect(received).toEqual(expected) // deep equality

    - Expected  - 1
    + Received  + 1

      Array [
    -   "0",
        "1",
    +   "1001",
        "2",
      ]

      178 |       expect(brokerPool.brokers).toEqual({})
      179 |       await brokerPool.refreshMetadata([topicName])
    > 180 |       expect(Object.keys(brokerPool.brokers).sort()).toEqual(['0', '1', '2'])
          |                                                      ^
      181 |       expect(Object.values(brokerPool.brokers)).toEqual(
      182 |         expect.arrayContaining([expect.any(Broker), expect.any(Broker), expect.any(Broker)])
      183 |       )

      at Object.<anonymous> (src/cluster/__tests__/brokerPool.spec.js:180:54)

As environment variables should always be strings anyways: Fix that by just always quoting all environment
variables, to reduce the mental load of having all of YAMLs arcane rules in ones head.

[Nevon]

Fun, only slightly related fact, I once worked on a product that had different features enabled in different countries. To manage this configuration, we were using YAML and simple lists of country codes. Something like this:

newFeatureEnabled:
  - se
  - fi
  - gb

At some point we added support for Norway:

newFeatureEnabled:
  - se
  - fi
  - gb
  - no

But to our great surprise, it didn't work in Norway. In fact, I seem to recall us having some issue after introducing Norway into this list. Turns out, our YAML parser helpfully converted the string no to the boolean value false, because that makes a lot of sense.

I don't love YAML.