Simplify configuration of artifact repository

# Summary

This is a (feature) request to simplify the configuration of the artifact repository.

Currently a configuration map like this is required:

```yaml
apiVersion: v1
kind: ConfigMap
metadata:
name: artifact-repository
data:
default: |
s3:
bucket: artifacts
endpoint: minio.company.com:9000
insecure: false
accessKeySecret:
name: my-minio-cred
key: accesskey
secretKeySecret:
name: my-minio-cred
key: secretke
```
See https://argoproj.github.io/argo-workflows/artifact-repository-ref/

I have several issues with this configuration layout:

1. The configuration key ("default") contains a complex multi-line value. That value is structured in a way that it looks like a fragment of a Kubernetes deployment. I had a lot of trouble to understand how this is supposed to work and it made my head hurt. It looks like a mix of specific configuration (e.g. a host name) and a Kubernetes deployment fragment to me. Yes, technically it is possible to put anything into such a configuration item but I don't think it's a good idea to do that if only a few parts of that value needs to be configurable by themself (like the name of the s3 host or the bucket). I think this should be simplified.

2. The structured value of the configuration key ("default") contains several environment-specific elements: "bucket", "endpoint", "insecure". Right now I don't see a good way to adjust just(!) these values to a specific deployment environment and leaving the rest of it untouched because the entire multi-line structure is just on single value.

3. The configuration element "s3.insecure" leads to redundancies. For some reason the configuration element "s3.endpoint" doesn't support a fully qualified host name. That means, even if I find a way to put everything into a config map with simple key-value pairs, since I'm using the same S3 endpoint for some tasks in my workflow as well (which actually require a fully qualified S3 endpint), I am now forced to define the "endpoint" twice: 1 time with "https://" and 1 time without it. I would love to see that I could just put the full-qualified S3 endpoint into that configuration without the need to deal with the "s3.insecure" element.

My goal (in general) is to keep a Kubernetes deployment as simple as possible and have an environment-independent workflow deployment and everything that is environment-specific is supposed to be contained in a config map like this:

```
[...]
ENDPOINT=https://minio.company.com:9000
BUCKET:artifacts
[...]
```

Right now, I don't know how I could do that with Argo (specifically with the artifact repository configuration).

In case I missed something, please enlighten me :) However, I would appreciate if you seriously consider these suggestions.

# Use Cases

In every workflow that uses artifacts and also needs to be generic to be deployed in different environments.

---

**Message from the maintainers**:

Love this enhancement proposal? Give it a 👍. We prioritise the proposals with the most 👍.

Start with the artifact repository reference linked in the issue and the Kubernetes ConfigMap example shown there. Define the desired configuration shape from the stated use case, including environment-specific bucket and endpoint values and support for a fully qualified S3 endpoint; done requires an agreed design and corresponding implementation coverage.

Written by the indexing model from the issue text.