Create a test to protect regressions of the debugger

[jxyang]

We need this because the multi-memory-region implementation has very fragile support for debugger. The test should ensure breakpoints in application and myst runtime (kernel + target + enc) can be reached.

[vtikoo]

There is a basic test in tests/gdb, which tests setting a breakpoint in application code. Can be augmented to set breakpoints in myst runtime components.