Use 0.28.1 build image and update go and alpine versions (grafana#8583)

**What this PR does / why we need it**:

- Use the 0.28.1 build image
- Update Go version to 1.20.1
- Use Alpine 3.16.4
- Fix linter issues due to updated govet in 1.20.1 
- Modify images to not create `/etc/nsswitch.conf` file anymore
(available by default on Alpine 3.16.4)
- Remove impossible test cases for `TestMemChunk_IteratorBounds`(see
grafana#8591 (comment) for
context)

Signed-off-by: Michel Hollands <michel.hollands@grafana.com>
Signed-off-by: Christian Haudum <christian.haudum@gmail.com>
Co-authored-by: Christian Haudum <christian.haudum@gmail.com>
Co-authored-by: DylanGuedes <djmgguedes@gmail.com>

production/helm/loki/src/helm-test/Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.18.5 as build
+FROM golang:1.20.1 as build
 
 # build via Makefile target helm-test-image in root
 # Makefile. Building from this directory will not be
@@ -7,7 +7,7 @@ COPY . /src/loki
 WORKDIR /src/loki
 RUN make clean && make BUILD_IN_CONTAINER=false helm-test
 
-FROM alpine:3.16.2
+FROM alpine:3.16.4
 RUN apk add --update --no-cache ca-certificates=20220614-r0
 COPY --from=build /src/loki/production/helm/loki/src/helm-test/helm-test /usr/bin/helm-test
 ENTRYPOINT [ "/usr/bin/helm-test" ]