Update Dockerfile syntax version to 1.16

[pdabelf5]

Proposed changes

Update Dockerfile syntax version to 1.16
https://docs.docker.com/build/buildkit/dockerfile-release-notes/

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

[javorszky]

Yep, checked that there are no more dockerfiles with

find . -type f -iname "*dockerfile*"

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 52.95%. Comparing base (ba9864f) to head (fa90ccd).
Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7898      +/-   ##
==========================================
+ Coverage   52.82%   52.95%   +0.13%     
==========================================
  Files          90       90              
  Lines       21671    21729      +58     
==========================================
+ Hits        11447    11506      +59     
+ Misses       9747     9746       -1     
  Partials      477      477              

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