[lldb/test] Move `platform process list` tests to its own directory (NFC)

Since the `platform process` commamnd has more tests now, this commits
separates each of the `platform process` subcommand's test in its own directory.

Differential Revision: https://reviews.llvm.org/D74836

Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>

diff --git a/lldb/test/API/commands/platform/process/Makefile b/lldb/test/API/commands/platform/process/list/Makefile
similarity index 100%
rename from lldb/test/API/commands/platform/process/Makefile
rename to lldb/test/API/commands/platform/process/list/Makefile

diff --git a/lldb/test/API/commands/platform/process/TestProcessList.py b/lldb/test/API/commands/platform/process/list/TestProcessList.py
similarity index 100%
rename from lldb/test/API/commands/platform/process/TestProcessList.py
rename to lldb/test/API/commands/platform/process/list/TestProcessList.py

diff --git a/lldb/test/API/commands/platform/process/main.cpp b/lldb/test/API/commands/platform/process/list/main.cpp
similarity index 100%
rename from lldb/test/API/commands/platform/process/main.cpp
rename to lldb/test/API/commands/platform/process/list/main.cpp