Update node version to 18.12.0 on complete image (#1657)

This puts us on to the latest LTS release of node.

Test by using a private location with Uptime to run a browser monitor.

changelog/fragments/1667243040-Upgrade-node-to-18.12.0.yaml

@@ -0,0 +1,31 @@
+# Kind can be one of:
+# - breaking-change: a change to previously-documented behavior
+# - deprecation: functionality that is being removed in a later release
+# - bug-fix: fixes a problem in a previous version
+# - enhancement: extends functionality but does not break or fix existing behavior
+# - feature: new functionality
+# - known-issue: problems that we are aware of in a given version
+# - security: impacts on the security of a product or a user’s deployment.
+# - upgrade: important information for someone upgrading from a prior version
+# - other: does not fit into any of the other categories
+kind: feature
+
+# Change summary; a 80ish characters long description of the change.
+summary: Upgrade node to 18.12.0
+
+# Long description; in case the summary is not enough to describe the change
+# this field accommodate a description without length limits.
+#description:
+
+# Affected component; a word indicating the component this changeset affects.
+component:
+
+# PR number; optional; the PR number that added the changeset.
+# If not present is automatically filled by the tooling finding the PR where this changelog fragment has been added.
+# NOTE: the tooling supports backports, so it's able to fill the original PR number instead of the backport PR number.
+# Please provide it if you are adding a fragment for a different PR.
+#pr: 1234
+
+# Issue number; optional; the GitHub issue related to this changeset (either closes or is part of).
+# If not present is automatically filled by the tooling with the issue linked to the PR number.
+#issue: 1234

dev-tools/packaging/templates/docker/Dockerfile.elastic-agent.tmpl

@@ -162,7 +162,7 @@ RUN echo \
 
 # Setup synthetics env vars
 ENV ELASTIC_SYNTHETICS_CAPABLE=true
-ENV NODE_VERSION=16.15.0
+ENV NODE_VERSION=18.12.0
 ENV PATH="$NODE_PATH/node/bin:$PATH"
 # Install the latest version of @elastic/synthetics forcefully ignoring the previously
 # cached node_modules, heartbeat then calls the global executable to run test suites

dev-tools/packaging/templates/docker/Dockerfile.tmpl

@@ -160,7 +160,7 @@ USER {{ .user }}
 # Setup synthetics env vars
 ENV ELASTIC_SYNTHETICS_CAPABLE=true
 ENV SUITES_DIR={{ $beatHome }}/suites
-ENV NODE_VERSION=16.15.0
+ENV NODE_VERSION=18.12.0
 ENV PATH="$NODE_PATH/node/bin:$PATH"
 # Install the latest version of @elastic/synthetics forcefully ignoring the previously
 # cached node_modules, heartbeat then calls the global executable to run test suites