Node EOL

[willmcvay]

Background context or User story:

We have a number of services that depend on Node 14 and 16 runtimes. Node 14 is EOL in April and 16 in Sept this year so we should urgently update to v18

Specification or Acceptance Criteria:

• Likely Serverless modules will need updating
• Some GH Actions rely on 14 (third party actions as well as our own workflows)
• CDK stacks should use the v18 runtime for Lambdas

[willmcvay]

FYI this is getting a bit urgent!