feat: rm leiningen

[erdos]

Tasks:

• Remove usage of Leiningen build tool in favor of tools.deps
• Introduce Kaocha test runner

TODO:

• build single JAR file (with pom.xml)
• build uberjar file (with manifest), ensure that standalone mode works.
• run clojure unit tests
• run clojure visual regression tests
• run java junit tests
• tests report results in XML format (no change here)
• build javadoc pages
• basic commands: clean, compile, jar, uberjar, etc.
• check: version numbering works as expected
• check: spec instrumentation works as expected
• publishing to Clojars works without any changes
• changes in documentation
• ...

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 93.75%. Comparing base (43bd502) to head (496693a).

Files	Patch %	Lines
src/stencil/spec.clj	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #164      +/-   ##
==========================================
+ Coverage   93.40%   93.75%   +0.34%     
==========================================
  Files          31       31              
  Lines        2093     2097       +4     
  Branches      100       93       -7     
==========================================
+ Hits         1955     1966      +11     
  Misses         38       38              
+ Partials      100       93       -7     

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