Add start_and_break_on decorator to simplify gdb tests

[gsingh93]

@start_and_break_on takes a binary to run, a list of breakpoints, and optionally arguments to pass to the binary. It performs the same setup start_binary does, but also adds the breakpoints and then continues the program. This lets us remove some boilerplate from tests, as shown in the plist tests.

[disconnect3d]

Why don't we make it a pytest fixture instead of a decorator?

[gsingh93]

Two reasons:

1. A function that the user could just import themselves is not a good pytest fixture. The way we use start_binary right now is not great. If we instead automatically started it for them and passed in the process object, that would be a better fixture, but then the user can't customize the binary, breakpoints, etc.
2. Even if we pass this function in as a fixture, the user still has to call it as one of the first things they do. Tests are usually better when the initialization has happened before the function is even called, which can be done with a decorator.

[gsingh93]

@disconnect3d lmk what you think. I prefer this approach and was going to migrate some other tests to it, but will wait until you let me know you're ok with it.

[disconnect3d]

@gsingh93 I think making it a decorator makes things more complex unnecessarily? Why not just a standard function call that would be called within the test function instead? Some tests could want to call it multiple times too.

Regarding fixtures, the fixtures are kinda broken bcoz we never run tests all together but instead we run them each one by one. Fixtures allows for 'session fixtures' where the fixture would be called once for all tests in a test session etc. Another good thing of fixtures is that u can yield in them and whatever code is after the yield will be executed after the test finishes, as a kind of 'destructor'. But yeah, maybe its not so needed here.