Run all tests using JDK 17

[hrothwell]

As described in comments in #1924 - changes made to the base pom.xml here (now also present in main) should allow building all modules using JDK 17. This was tested locally using a local JDK 8 installation and JDK 17 installation, both builds pass locally. I did need to tweak the JDK 8 check locally to make sure it ran the proper JDK 8 if statement, but that shouldn't impact much if anything.

Should fix #892

Category (place an x in each of the [ ])

• bolt (Bolt for Java)
• bolt-{sub modules} (Bolt for Java - optional modules)
• slack-api-client (Slack API Clients)
• slack-api-model (Slack API Data Models)
• slack-api-*-kotlin-extension (Kotlin Extensions for Slack API Clients)
• slack-app-backend (The primitive layer of Bolt for Java)

Requirements

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.75%. Comparing base (71b0372) to head (1621e0a).

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #1296   +/-   ##
=========================================
  Coverage     74.75%   74.75%           
  Complexity     4141     4141           
=========================================
  Files           442      442           
  Lines         13062    13062           
  Branches       1317     1317           
=========================================
  Hits           9765     9765           
  Misses         2534     2534           
  Partials        763      763           

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[seratch]

Cool, cool! Thanks for sending this PR!