Fix and simplify checkmetrics make target (#1731)

The checkmetrics target currently uses promtool v2.5.0 which doesn't
include many improvements done over the time. This change also
simplifies the promtool installation, avoiding a temporary directory by
extracting the file directly to the target destination.

Signed-off-by: Tobias Schmidt <tobidt@gmail.com>

checkmetrics.sh

@@ -5,14 +5,12 @@ if [[ ( -z "$1" ) || ( -z "$2" ) ]]; then
     exit 1
 fi
 
-# Only check node_exporter's metrics, as the Prometheus Go client currently
-# exposes a metric with a unit of microseconds.  Once that is fixed, remove
-# this filter.
-lint=$($1 check metrics < $2 2>&1 | grep "node_")
+# Ignore known issues in auto-generated and network specific collectors.
+lint=$($1 check metrics < "$2" 2>&1 | grep -v -E "^node_(entropy|memory|netstat|wifi_station)_")
 
-if [[ ! -z $lint ]]; then
+if [[ -n $lint ]]; then
     echo -e "Some Prometheus metrics do not follow best practices:\n"
     echo "$lint"
 
     exit 1
-fi
+fi