aws-for-fluent-bit: provide realistic runAsNonRoot security context values

Provide realistic values for running fluent-bit as a non-root user:

I am not sure what securityContext Fluent Bit needs to run correctly.
Once this is change is in a think a separate PR could be used to determine
what a default standard policy should look like.

_Originally posted by @razorsk8jz in https://github.com/aws/eks-charts/pull/923#discussion_r1142587589_

The security context comments in values.yaml are not usable:

```yaml
podSecurityContext: {}
# runAsUser: 1000
# runAsGroup: 1000
# runAsNonRoot: true
# seccompProfile:
# type: RuntimeDefault
containerSecurityContext: {}
# allowPrivilegeEscalation: false
# capabilities:
# drop:
# - ALL
```

Issues:
1. The user and group ids do not exist in the aws-for-fluent-bit image. AFAICT the image is based on amazonlinux/scratch and does not define any non-root users.
2. All the files in the image are owned by 0:0 (root) so runAsNonRoot probably won't suffice, at least not without some additional capabilities, such as FOWNER
3. Typical deployments will enable storage.path (e.b., /var/fluent-bit/state/flb-storage/), which appears to need a hostPath

Related:
* https://github.com/fluent/fluent-bit/issues/872
* https://docs-bigbang.dso.mil/1.56.0/docs/understanding-bigbang/package-architecture/fluentbit/#Storage
* https://repo1.dso.mil/big-bang/product/packages/fluentbit/-/blob/main/chart/values.yaml

https://github.com/aws/eks-charts/issues/719

Start with the aws-for-fluent-bit chart's values.yaml and inspect the image's users, file ownership, and storage.path behavior. Review the related Fluent Bit issue and deployment examples to determine what non-root security context and hostPath requirements are supported. Done means the commented values are realistic and usable for common deployments.

Written by the indexing model from the issue text.