[LLDB] Impove ObjectFileELF's .dynamic parsing and usage. (llvm#102570)

This patch improves the ability of a ObjectFileELF instance to read the
.dynamic section. It adds the ability to read the .dynamic section from
the PT_DYNAMIC program header which is useful for ELF files that have no
section headers and for ELF files that are read from memory. It cleans
up the usage of the .dynamic entries so that
ObjectFileELF::ParseDynamicSymbols() is the only code that parses
.dynamic entries, teaches that function the read and store the string
values for each .dynamic entry. We now dump the .dynamic entries in the
output of "image dump objfile". It also cleans up the code that gets the
dynamic string table so that it can grab it from the DT_STRTAB and
DT_STRSZ .dynamic entries for when we have a ELF file with no section
headers or we are reading it from memory.

Author: clayborg

lldb/include/lldb/Symbol/ObjectFile.h

@@ -656,8 +656,9 @@ class ObjectFile : public std::enable_shared_from_this<ObjectFile>,
   // When an object file is in memory, subclasses should try and lock the
   // process weak pointer. If the process weak pointer produces a valid
   // ProcessSP, then subclasses can call this function to read memory.
-  static lldb::DataBufferSP ReadMemory(const lldb::ProcessSP &process_sp,
-                                       lldb::addr_t addr, size_t byte_size);
+  static lldb::WritableDataBufferSP
+  ReadMemory(const lldb::ProcessSP &process_sp, lldb::addr_t addr,
+             size_t byte_size);
 
   // This function returns raw file contents. Do not use it if you want
   // transparent decompression of section contents.