feat: support resolve symbols in mini debug info(".gnu_debugdata")

[zmj64351508]

Mini debug info is stored in a lzma-compressed section named ".gnu_debugdata" in elf. More information can be found in https://archive.fosdem.org/2020/schedule/event/debugging_mini/attachments/slides/4059/export/events/attachments/debugging_mini/slides/4059/fosdem2020_minidebuginfo_kkleine.pdf

When it fails to get symbol in ".symtab", it will try to find the ".gnu_debugdata" section, uncompressing it and read the data as another elf to get the real "symtab" and "dynsym". (note: even if ".dynsym" exists, ".gnu_debugdata" can store more symbols)

Unfortunately, the original MMapedElfFile can't accept an in-memory area as the data of elf file. To reuse the original code to get the symbols, some changes are made:

1. elfmmap.go is split into 2 structs(files):
   a. the origin struct MMapedElfFile
   b. the new struct InMemElfFile, which is responsible to parse elf for the uncompressed .gnu_debugdata. The original MMapedElfFile also reuse this struct to read elf.
2. A new interface ElfSymbolReader, which is used by struct SymbolTable to get the symbol string.
3. A new struct SymbolTableWithMiniDebugInfo to combine symbols in original elf and mini debug elf.
4. A new interface SymbolTableInterface to abstract SymbolTable and SymbolTableWithMiniDebugInfo.

[korniltsev]

I will take a look into the PR some time later this week. Please add at least one test extracting symbols from this mini debug info

[zmj64351508]

PR Updated, including test

[korniltsev]

Thanks. I will be able to take a look next week.

[korniltsev]

thanks