[test] Add new CLI testing platform

Adds the new CLI testing platform that I'm proposing.
See the added `README.md` for details.

tests/cli-tests/basic/help.sh

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+#!/bin/sh -e
+println "+ zstd -h"
+zstd -h
+println "+ zstd -H"
+zstd -H
+println "+ zstd --help"
+zstd --help

tests/cli-tests/basic/help.sh.stdout.glob

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++ zstd -h
+*** zstd command line interface *-bits v1.*.*, by Yann Collet ***
+Usage :
+      zstd *args* *FILE(s)* *-o file*
+
+FILE    : a filename
+          with no FILE, or when FILE is - , read standard input
+Arguments :
+ -#     : # compression level*
+ -d     : decompression
+ -D DICT: use DICT as Dictionary for compression or decompression
+ -o file: result stored into `file` (only 1 output file)
+ -f     : disable input and output checks. Allows overwriting existing files,
+          input from console, output to stdout, operating on links,
+          block devices, etc.
+--rm    : remove source file(s) after successful de/compression
+ -k     : preserve source file(s) (default)
+ -h/-H  : display help/long help and exit
+
+Advanced arguments :
+ -V     : display Version number and exit
+...
++ zstd -H
+...
+Arguments :
+...
+Advanced arguments :
+...
++ zstd --help
+...
+Arguments :
+...
+Advanced arguments :
+...

tests/cli-tests/basic/version.sh

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+#!/bin/sh -e
+zstd -V
+zstd --version

tests/cli-tests/basic/version.sh.stdout.glob

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+*** zstd command line interface *-bits v1.*.*, by Yann Collet ***
+*** zstd command line interface *-bits v1.*.*, by Yann Collet ***