Adopt distroless as container base image

[vmercierfr]

Objective

Reduce attack surface

Why

Prometheus RDS exporter is deployed using alpine container base image. Although this image is minimalist, it contains around 200 binaries that are not required to run the application and increase its attack surface.

Kubernetes project adopted distroless few years ago to limit container image content to application and its runtime.

In addition to safety benefits, the container image is reduced by 9% (53MB to 48MB).

	dive
Before
After

How

• Update container image to use distroless instead of alpine base image
• Set HEALTHCHECK to None as curl is no more installed (See Healthcheck fails in Alpine container: curl not found #249)
• Update local development to use Go 1.23 (fix) and distroless
• Add distroless to contributing guide

Release

• Merge this PR

[vmercierfr]

This will conflicts with #249. But sounds HEALTHCHECK is only supported by Docker (desktop?) engine and probably not relevant for production deployment these days.

So I will recommend to just remove HEALTHCHECK instruction in favor of attack surface reduction.