Fix abbreviation output for predicate mismatches

[FranciscoMaxwell]

Summary

• make the abbreviation ellision marker comparable on the JVM so pretty-printing can handle abbreviated maps with mixed keys
• add a regression test for the *use-abbreviation* predicate mismatch case from matcher-combinators.config/*use-abbreviation* throws error when actual doesn't match #234

Closes #234.

Testing

• deps.exe -M:dev:clj-test .repro-234.clj with a temporary local runner: confirmed the matcher-combinators.config/*use-abbreviation* throws error when actual doesn't match #234 reproduction returns a printable string without throwing
• deps.exe -M:dev:clj-test -e "(require 'matcher-combinators.config-test) (println :loaded)"
• deps.exe -A:dev:clj-test:test-runner -n matcher-combinators.config-test was also attempted; the new regression ran, but existing assertions in that namespace fail on Windows because printer/as-string returns CRLF (\r\n) while the expected strings use LF (\n)