The System.console() method is intended to indicate whether the
JVM process is running with stdio connected to a TTY-like, but in
JDK 22 through 24, it also returns non-null for non-TTY stdio due
to the use of JLine as a pseudo-terminal. This behavior changed
back to JDK 21 behavior in JDK 25, but we must continue double-
checking Console.isTerminal() for situations where the JLine logic
is live.

Part of improvements for jruby#9590.

See https://bugs.openjdk.org/browse/JDK-8361911 for an OpenJDK
issue that details the changing behavior of System.console().

If JRuby is started through Main, then the stdio channels we set up
are either native or come from the JVM's System.in/out/err. In the
latter case, we can use the JVM's System.console() and
Console.isTerminal() methods to indicate if the JRuby stdio is a
TTY. This fixes previous logic that always assumed any non-native
stdio was conneected to a TTY, leading to cases where embedded use
might incorrectly assume that color console output or hard process
exits were appropriate.

Fixes jruby#9590

See jruby#9590