drop node 12 support and bump node version used in containers

[trentm]

Node v12 goes out of maint at the end of Apr 2022. Should we drop support for it? Should we bump the uses of node v12? Some relevant hits in the current source code:

package.json
22:    "node": ">=12"

.github/workflows/lint.yml
20:        node-version: '14'

docker-compose.yml
160:    image: node:12-bullseye

docker-compose-elastic-cloud.yml
110:    image: node:12-bullseye

.ci/bump-version.sh
13:  node:12-alpine /bin/sh -c "set -x

Makefile
4:LTS_ALPINE ?= 12-alpine

See also:

• #129 brings up potential dependency issues if the docker-compose files are bumped to node 16 or later for the postgres database load container
• #153 is bumping the default Dockerfile to use node-18 for the app