Decode "Line" chunk and expand line instructions

[dumbbell]

Line information comes from the "Line" chunk in the beam module. This is not decoded by beam_disasm and the line instructions it produces only have the index inside that "Line" beam chunk.

So far, we needed to get rid of all those line instructions because they were invalid for the compiler. It meant that frames in stacktraces pointing to an extracted function had no location. This made any sort of debugging quite difficult.

Here is an example without this patch:

%% Based on the following function:
%%     crashing_fun() ->
%%         throw("Expected crash").

1> Fun = khepri_fun:to_standalone_fun(fun mod:crashing_fun/0, #{}).
2> khepri_fun:exec(Fun, []).
** exception throw: "Expected crash"
     in function  kfun__mod__crashing_fun__33048370:run/0

Now, we decode the "Line" beam chunk for each module we need to disassemble. We then use this decoded table to replace the incomplete line instructions by valid ones.

Thanks to that, we get stacktrace frames with correct locations, making debugging far easier. Here is the same example as above, but with this change in place:

1> Fun = khepri_fun:to_standalone_fun(fun mod:crashing_fun/0, #{}).
2> khepri_fun:exec(Fun, []).
** exception throw: "Expected crash"
     in function  kfun__mod__crashing_fun__33048370:run/0 (.../mod.erl, line 30)

Fixes #50.

[coveralls]

Pull Request Test Coverage Report for Build 359

• 57 of 66 (86.36%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.1%) to 85.46%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/khepri_fun.erl	57	66	86.36%

Totals
Change from base Build 357:	0.1%
Covered Lines:	1534
Relevant Lines:	1795

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💛 - Coveralls