Add support for loading debug information from debuginfod

[XVilka]

Fedora 35 release that is scheduled to the end of 2021 will use Debuginfod by default for storing debug information for the binaries:

• https://fedoraproject.org/wiki/Changes/DebuginfodByDefault

With GNU Binutils 2.34 comes debuginfod support, which is the HTTP server catching our eye while the debuginfod server is distributed as part of the latest elfutils package. This isn't for a general purpose web server thankfully but is an HTTP server for distributing ELF/DWARF debugging information and source code. With debuginfod enabled, Binutils' readelf and objdump utilities can query the HTTP server(s) for debug files that cannot otherwise be found. Enabling this option requires building Binutils using --with-debuginfod.

See https://developers.redhat.com/blog/2019/10/14/introducing-debuginfod-the-elfutils-debuginfo-server/ for more information.

• https://sourceware.org/elfutils/Debuginfod.html
• Ubuntu Linux https://ubuntu.com/server/docs/service-debuginfod
• Debian Linux https://wiki.debian.org/Debuginfod
• Fedora Linux https://fedoraproject.org/wiki/Debuginfod
• Arch Linux https://wiki.archlinux.org/title/Debuginfod

Depends on #1805

Originally posted by @XVilka in #907 (comment)

[XVilka]

LLVM added support for Debuginfod as well: llvm/llvm-project@36f0190

[wargio]

probably should be worth to use this with flirt, so we can easily create signatures from this.

[ret2libc]

@XVilka I guess we should postpone this to 0.7.0, right? I don't think there's a way this is gonna lend before it.