Split test cases out of TestLldbGdbServer.py and TestGdbRemoteFork.py
into separate files to avoid hitting the 600s timeout limit. The
inferior used by these tests (main.cpp) takes approximately 20s to
compile with a Debug build of clang, causing timeouts when a single test
file contains many tests. By grouping similar tests into separate files,
we can prevent timeouts and improve overall test efficiency.
