CLI feature: generate commands for shell to source for environment

[marktsuchida]

cjdk env should print something like

CJDK_ORIGINAL_JAVA_HOME="$JAVA_HOME"
CJDK_ORIGINAL_PATH="$PATH"
JAVA_HOME=/path/to/jdk
PATH="$JAVA_HOME/bin:$PATH"

except that the output should be tailored to the current shell/cmd.exe/powershell. In bash, this can be used as

. $(cjdk --jdk 17 env)

cjdk env --restore should restore the previous state.

[marktsuchida]

Also cjdk env --no-add-bin, corresponding to cjdk.java_env(add_bin=False).

[ctrueden]

Would an optional argument to env to specify the flavor explicitly make sense? Something like cjdk env --flavor=sh, cjdk env --flavor=powershell, etc. Still autodetecting the current shell type by default of course.