Create an lldb-dap fuzzer

[JDevlieghere]

Create a fuzzer for lldb-dap, similar to clangd-fuzzer. We already have various fuzzers in LLDB.

A few observations after briefly looking into this:

• We'll need to turn most of LLDB DAP into a library, which means moving all but the driver code out of lldb-dap.cpp and having the latter link that library.
• We should add the fuzzer as a subdirectory in lldb-dap rather than lldb-fuzzer so it can access the new DAP library.

[llvmbot]

@llvm/issue-subscribers-lldb-dap

Author: Jonas Devlieghere (JDevlieghere)

Create a fuzzer for lldb-dap, similar to [clangd-fuzzer](https://github.com/llvm/llvm-project/tree/main/clang-tools-extra/clangd/fuzzer). We already have [various fuzzers](https://github.com/llvm/llvm-project/tree/main/lldb/tools/lldb-fuzzer) in LLDB.

A few observations after briefly looking into this:

• We'll need to turn most of LLDB DAP into a library, which means moving all but the driver code out of lldb-dap.cpp and having the latter link that library.
• We should add the fuzzer as a subdirectory in lldb-dap rather than lldb-fuzzer so it can access the new DAP library.