chore(NODE-6635): pin NPM to 10 when Node version is 18

.evergreen/config.yml

@@ -140,6 +140,7 @@ buildvariants:
       packager_distro: ubuntu2204
       packager_arch: x86_64
       NODE_LTS_VERSION: "18"
+      NPM_VERSION: "10"
     tasks:
       - run-tests-ubuntu
       - run-tests-ubuntu-rtld
@@ -185,6 +186,7 @@ buildvariants:
       packager_distro: ubuntu2204
       packager_arch: arm64
       NODE_LTS_VERSION: "18"
+      NPM_VERSION: "10"
     tasks:
       - run-tests-ubuntu
       - run-tests-ubuntu-rtld

.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=${NODE_LTS_VERSION:-14}
-# npm version can be defined in the environment for cases where we need to install
-# a version lower than latest to support EOL Node versions.
-export NPM_VERSION=${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
 
 echo "Installing Node.js $NODE_LTS_VERSION with npm@$NPM_VERSION"