use Lambda SnapStart to speed up cold starts

[hrodmn]

I tested Lambda SnapStart out in maap-eoapi and it reduced the cold start time of the titiler-pgstac /healthz endpoint from ~6.4 seconds to ~1.5 seconds.

For any given Lambda, the changes required are:

• Upgrade the runtime to at least Python 3.12
  • for titiler-pgstac you need to make sure libexpat.so.1 is available in LD_LIBRARY_PATH because it is not available by default in the Python 3.12 runtime
• Add snapStart: lambda.SnapStartConf.ON_PUBLISHED_VERSIONS to the Lambda construct
• Point the HttpLambdaIntegration at a registered version of the Lambda function
• Update the handler with runtime hooks that determine specific things to do before taking the snapshot and after loading from a snapshot.