Replace Java 8 with newer LTS Java 17

[exoego]

Closes #2746

Unfortunately, not a small number of libraries used in Scala Steward dropped Java 8.
Since scala-steward is not a library, I think long-term Java 8 support is not needed fundamentally.

[codecov]

Codecov Report

Base: 80.58% // Head: 80.58% // No change to project coverage 👍

Coverage data is based on head (b9d4718) compared to base (b9d4718).
Patch has no changes to coverable lines.

❗ Current head b9d4718 differs from pull request most recent head 4c726d7. Consider uploading reports for the commit 4c726d7 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2779   +/-   ##
=======================================
  Coverage   80.58%   80.58%           
=======================================
  Files         149      149           
  Lines        2849     2849           
  Branches      198      198           
=======================================
  Hits         2296     2296           
  Misses        553      553           

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[alejandrohdezma]

Shouldn't we do the same with Java 11 and only support 17?

[exoego]

@alejandrohdezma
That is a good point.
I want to propose "last two LTS" strategy so it gives some time to prepare to users.
WDYT?

[alejandrohdezma]

Yeah, sounds like a sensible idea 😸