Add support for attaching uprobes and uretprobes to offsets

[rafaelroquetto]

In its core, this PR adds support for attaching ebf programs to (start and return) offsets, in the same fashion done for "goprobes". The motivation is also the same: uretprobes attachments can be unreliable in contexts where the target process stack changes. In such scenarios, attaching uretprobes may cause the target process to crash.

Under the hood, we scan the target binary for the offsets of the symbols we want to attach to: the start offset, and the offset of every RET instruction present in that function. This approach is not flawless, and will fail if the the function/symbol in question does not posses any RET instruction due to compiler optimisations (see here for an example).

Due to the requirement of handling uprobe offsets, codewise the handling of uprobes and goprobes becomes less distinct. The ultimate goal would be to merge their corresponding code and remove considerable code duplication. A central piece for this is the repurposing of ebpfcommon.FuncPrograms into a more comprehensive data structure that carries the entire context (relevant to our use cases) of ebpf attachments: apart from the start and end programs, it now features the symbol name and the offsets. This also enables us to ditch a few maps that were being used for this purpose, and simplifies the code considerably.

[codecov]

Codecov Report

Attention: Patch coverage is 77.04918% with 70 lines in your changes missing coverage. Please review.

Project coverage is 80.93%. Comparing base (21f9154) to head (1e50a27).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/internal/ebpf/instrumenter.go	71.06%	31 Missing and 15 partials ⚠️
pkg/internal/ebpf/generictracer/generictracer.go	87.64%	7 Missing and 4 partials ⚠️
pkg/internal/goexec/instructions.go	58.33%	3 Missing and 2 partials ⚠️
pkg/internal/ebpf/httptracer/httptracer.go	57.14%	3 Missing ⚠️
pkg/internal/ebpf/tctracer/tctracer.go	57.14%	3 Missing ⚠️
pkg/internal/ebpf/gotracer/gotracer.go	80.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1419      +/-   ##
==========================================
- Coverage   81.07%   80.93%   -0.14%     
==========================================
  Files         149      149              
  Lines       15130    15250     +120     
==========================================
+ Hits        12266    12342      +76     
- Misses       2272     2301      +29     
- Partials      592      607      +15     

Flag	Coverage Δ
integration-test	59.83% <71.47%> (+0.08%)	⬆️
k8s-integration-test	59.35% <75.73%> (-1.24%)	⬇️
oats-test	33.92% <66.55%> (+0.28%)	⬆️
unittests	51.92% <24.26%> (+0.23%)	⬆️

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[grcevski]

LGTM! Very cool refactor and so nice to see we use the same mechanism now for Go and non-Go.