argument parser: use CLI11 and add unit tests

CLI11 is one of the most commonly use argument parser in OpenBMC. It can
save ~150 lines of codes in this project.

We are hitting argument related bugs that not covered in unit tests.
This test adds a test for argument parsing.

Tested: QEMU IPMI/Redfish worked.

Signed-off-by: Nan Zhou <nanzhoumails@gmail.com>
Change-Id: Ib409c7e6a82ad31049f2da3e32727ebdf185f0fc
diff --git a/.gitignore b/.gitignore
index 4524188..db7a4a0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,3 +4,4 @@
 !subprojects/phosphor-logging.wrap
 !subprojects/sdbusplus.wrap
 !subprojects/sdeventplus.wrap
+!subprojects/cli11.wrap