uprobe: improve C++ probes listing

[viktormalik]

When listing probes with the new :cpp prefix, demangle function names.

Example:

# bpftrace -l 'uprobe:/my/prog:*'
uprobe:/my/prog:_Z3funi
uprobe:/my/prog:_ZN3Bar3funEv
uprobe:/my/prog:_ZN3Foo3funEv

# bpftrace -l 'uprobe:/my/prog:cpp:*'
uprobe:/my/prog:cpp:"fun(int)"
uprobe:/my/prog:cpp:"Bar::fun()"
uprobe:/my/prog:cpp:"Foo::fun()"

Note: we need to surround the demangled name with quotes as it may contain some symbols which won't be accepted by the attach point parser (e.g. :: or ()). With quotes, the listing entries can be directly used as attach points.

Second note: I didn't add any tests for this b/c we don't have support for C++ testing programs and it didn't make sense to add it (could be quite a lot of changes in CMake) for this simple thing.

Checklist

• Language changes are updated in man/adoc/bpftrace.adoc and if needed in docs/reference_guide.md
• User-visible and non-trivial changes updated in CHANGELOG.md
• The new behaviour is covered by tests