Add module/funcs to support the new ltest runner

[oubiwann]

This ticket blocks lfe-deprecated/lfetool#160

Output example:

• lfex/ltest@c107d65#commitcomment-9232105

Code has landed in ltest master:

• https://github.com/lfex/ltest/commits/master

ltest has a make target that runs this test runner:

check-runner-ltest: compile-no-deps compile-tests
        @clear
        @PATH=$(SCRIPT_PATH) ERL_LIBS=$(ERL_LIBS) \
        erl -cwd "`pwd`" -listener ltest-listener -eval \
        "case 'ltest-runner':all() of ok -> halt(0); _ -> halt(127) end" \
        -noshell

Create a new ltool-cli module to house the functions for this.

[oubiwann]

This work has been done in ltest.