libsysprof-analyze: give shape to ELF loading APIs

We need to separate a number of concerns here, such as debug-dirs within
the process namespace vs global debug-dirs (external symbols on a developer
workstation vs IoT/Laptop/VM/alternate-device).

That means we need to be able to resolve paths via the mount namespace of
the process as it was seen in the capture file.

Additionally, we need to follow .gnu_debuglink section headers so that we
can associate the version with symbols with the ELF that is loaded from
the processes SysprofAddressLayout.

src/libsysprof-analyze/meson.build

@@ -30,6 +30,8 @@ libsysprof_analyze_private_sources = [
   'sysprof-address-layout.c',
   'sysprof-document-bitset-index.c',
   'sysprof-document-symbols.c',
+  'sysprof-elf.c',
+  'sysprof-elf-loader.c',
   'sysprof-mount.c',
   'sysprof-mount-device.c',
   'sysprof-mount-namespace.c',