Use alpine base for lib-injection image

`libdl.so.2: cannot open shared object file: No such file or directory`
errors have been reported in customer environments which prevents
application containers from starting up when using [library
injection](https://docs.datadoghq.com/tracing/trace_collection/library_injection_local/?tab=kubernetes#step-3---tag-your-pods-with-unified-service-tags).
Likely this is due to some other software such as instrumentation or
security that modifies the command run in the container.

`busybox` [lacks many standard C
libraries](docker-library/busybox#46).

`alpine` is a similarly sized image which does provide the standard C
libraries which mitigates the issue

There is little risk in changing the base image to `alpine` as the only
command required is to copy files from the image to a volume. It is
possible that the command that is being added to the container is not
compatible with alpine images.

Change the base image from `busybox` to `alpine` to make the image more
compatible with other software environments.

Author: Kyle-Verhoog

Diff for: .github/workflows/lib-injection.yaml

@@ -33,7 +33,7 @@ jobs:
     - name: Set up Docker platforms
       id: buildx-platforms
       run:  |
-        BUILDX_PLATFORMS=`docker buildx imagetools inspect --raw busybox:latest | jq -r 'reduce (.manifests[] | [ .platform.os, .platform.architecture, .platform.variant ] | join("/") | sub("\\/$"; "")) as $item (""; . + "," + $item)' | sed 's/,//'`
+        BUILDX_PLATFORMS=`docker buildx imagetools inspect --raw alpine:3.18.3 | jq -r 'reduce (.manifests[] | [ .platform.os, .platform.architecture, .platform.variant ] | join("/") | sub("\\/$"; "")) as $item (""; . + "," + $item)' | sed 's/,//'`
         echo "$BUILDX_PLATFORMS"
         echo "platforms=$BUILDX_PLATFORMS" >> $GITHUB_OUTPUT
 

Diff for: lib-injection/Dockerfile

@@ -1,7 +1,7 @@
 FROM scratch AS java_agent
 COPY dd-java-agent.jar /
 
-FROM busybox
+FROM alpine:3.18.3
 
 ARG UID=10000
 RUN addgroup -g 10000 -S datadog \