When LLDB Python bindings are used and stack backtraces are enabled
for logging, getMainExecutable() is called with argv0 being null.
This caused the fallback function getprogpath() (used on FreeBSD, NetBSD
and Linux) to segfault. Make it handle null executable name gracefully.
Differential Revision: https://reviews.llvm.org/D91012
Summary: Moves lldbsuite tests to lldb/test/API.
This is a largely mechanical change, moved with the following steps:
```
rm lldb/test/API/testcases
mkdir -p lldb/test/API/{test_runner/test,tools/lldb-{server,vscode}}
mv lldb/packages/Python/lldbsuite/test/test_runner/test lldb/test/API/test_runner
for d in $(find lldb/packages/Python/lldbsuite/test/* -maxdepth 0 -type d | egrep -v "make|plugins|test_runner|tools"); do mv $d lldb/test/API; done
for d in $(find lldb/packages/Python/lldbsuite/test/tools/lldb-vscode -maxdepth 1 -mindepth 1 | grep -v ".py"); do mv $d lldb/test/API/tools/lldb-vscode; done
for d in $(find lldb/packages/Python/lldbsuite/test/tools/lldb-server -maxdepth 1 -mindepth 1 | egrep -v "gdbremote_testcase.py|lldbgdbserverutils.py|socket_packet_pump.py"); do mv $d lldb/test/API/tools/lldb-server; done
```
lldb/packages/Python/lldbsuite/__init__.py and lldb/test/API/lit.cfg.py were also updated with the new directory structure.
Reviewers: labath, JDevlieghere
Tags: #lldb
Differential Revision: https://reviews.llvm.org/D71151
