start-all.sh: Validate files in target and support es-linus

This patch address multiple issues when using the `--target-directory`
option.

1. Fix a documentation bug, that uses the wrong file name for scylla
   targets.
2. Add validation step that validate that all target files are inside
   the directory.
3. Add an option for SE-Linux to bind the directory correctly.

Fixes #2398

Signed-off-by: Amnon Heiman <amnon@scylladb.com>
(cherry picked from commit f0070af)

start-all.sh

@@ -99,7 +99,7 @@ Options:
   --enable-protobuf              - If set, enable the experimental Prometheus Protobuf with Native histograms support.
   --scrap [scrap duration]       - Change the default Prometheus scrap duration. Duration is in seconds.
   --target-directory             - If set, prometheus/targets/ directory will be set as a root directory for the target files
-                                   the file names should be scylla_server.yml, node_exporter_servers.yml, and  scylla_manager_servers.yml
+                                   the file names should be scylla_servers.yml, node_exporter_servers.yml, scylla_manager_agents.yml, and scylla_manager_servers.yml
   --stack id                     - Use this option when running a secondary stack, id could be 1-4
   --limit container,param        - Allow to set a specific Docker parameter for a container, where container can be:
                                    prometheus, grafana, alertmanager, loki, sidecar, grafanarender
@@ -578,7 +578,19 @@ else
 fi
 
 if [ "$TARGET_DIRECTORY" != "" ]; then
-    SCYLLA_TARGET_FILE="-v "$($readlink_command $TARGET_DIRECTORY)":/etc/scylla.d/prometheus/targets/"
+    SCYLLA_TARGET_FILE="-v "$($readlink_command $TARGET_DIRECTORY)":/etc/scylla.d/prometheus/targets/:z"
+    if [ ! -f $TARGET_DIRECTORY/scylla_servers.yml ]; then
+        echo "Warning, using $TARGET_DIRECTORY for Prometheus traget directory, scylla_servers.yml is missing, make sure to create it, or ScyllaDB targets will be missing"
+    fi
+    if [ ! -f $TARGET_DIRECTORY/node_exporter_servers.yml ]; then
+        echo "Warning, using $TARGET_DIRECTORY for Prometheus traget directory, node_exporter_servers.yml is missing, make sure to create it, or node-exporter targets will be missing"
+    fi
+    if [ ! -f $TARGET_DIRECTORY/scylla_manager_agents.yml ]; then
+        echo "Warning, using $TARGET_DIRECTORY for Prometheus traget directory, scylla_manager_agents.yml is missing, make sure to create it, or ScyllaDB manager-agent targets will be missing"
+    fi
+    if [ ! -f $TARGET_DIRECTORY/scylla_manager_servers.yml ]; then
+        echo "Warning, using $TARGET_DIRECTORY for Prometheus traget directory, scylla_manager_servers.yml is missing, make sure to create it, or ScyllaDB manager target will be missing"
+    fi
 fi
 if [ -z $DATA_DIR ]
 then