chore(NODE-6634): pin NPM to 10 when Node version is 18

.evergreen/install-dependencies.sh

@@ -6,9 +6,15 @@ set -o errexit  # Exit the script with error if any of the commands fail
 ## 'latest'
 ## a full nodejs version, in the format v<major>.<minor>.patch
 export NODE_LTS_VERSION=${NODE_LTS_VERSION:-16}
-# npm version can be defined in the environment for cases where we need to install
-# a version lower than latest to support EOL Node versions.
-export NPM_VERSION=${NPM_VERSION:-latest}
+# If NODE_LTS_VERSION is numeric and less than 18, default to 9, if less than 20, default to 10.
+# Do not override if it is already set.
+if [[ "$NODE_LTS_VERSION" =~ ^[0-9]+$ && "$NODE_LTS_VERSION" -lt 18 ]]; then
+    export NPM_VERSION=${NPM_VERSION:-9}
+elif [[ "$NODE_LTS_VERSION" =~ ^[0-9]+$ && "$NODE_LTS_VERSION" -lt 20 ]]; then
+    export NPM_VERSION=${NPM_VERSION:-10}
+else
+    export NPM_VERSION=${NPM_VERSION:-latest}
+fi
 
 source $DRIVERS_TOOLS/.evergreen/install-node.sh