chore: pin all cli test FROM lines to linux/amd64 (#2137)

Many of these images have a slightly different sets of packages when the
arm64 variant is pulled, so that leaving this digest unpinned causes the
tests to fail on arm64 hosts. Pin the FROM lines to force stable
platform values regardless of host architecture.

Signed-off-by: Will Murphy <will.murphy@anchore.com>

test/cli/test-fixtures/image-bad-binaries/Dockerfile

@@ -1,4 +1,4 @@
-FROM debian:sid
+FROM debian:sid@sha256:bee393b48f83fdeb978ce68abb9dc955d6398b984fca88b52a09dceb45ac74b5
 ADD sources.list /etc/apt/sources.list.d/sources.list
 RUN apt update -y && apt install -y dpkg-dev
 # this as a "macho-invalid" directory which is useful for testing

test/cli/test-fixtures/image-hidden-packages/Dockerfile

@@ -1,4 +1,4 @@
-FROM centos:7.9.2009
+FROM centos:7.9.2009@sha256:dead07b4d8ed7e29e98de0f4504d87e8880d4347859d839686a31da35a3b532f
 # all-layers scope should pickup on vsftpd
 RUN yum install -y vsftpd
-RUN yum remove -y vsftpd
+RUN yum remove -y vsftpd

test/cli/test-fixtures/image-java-spdx-tools/Dockerfile

@@ -1,4 +1,4 @@
-FROM openjdk:11
+FROM openjdk:11@sha256:e81b7f317654b0f26d3993e014b04bcb29250339b11b9de41e130feecd4cd43c
 
 RUN wget --no-verbose https://github.com/spdx/tools-java/releases/download/v1.1.3/tools-java-1.1.3.zip && \
 	unzip tools-java-1.1.3.zip && \

test/cli/test-fixtures/image-node-binary/Dockerfile

@@ -1 +1 @@
-FROM node:19-alpine3.15
+FROM node:19-alpine3.15@sha256:07050181369f52460e788738272bcb22b71c7cfc6fafee0b5cd27d2022513a86

test/cli/test-fixtures/registry/Dockerfile

@@ -1 +1 @@
-FROM alpine:latest
+FROM alpine@sha256:c5c5fda71656f28e49ac9c5416b3643eaa6a108a8093151d6d1afc9463be8e33