Add new API in SBTarget for loading core from SBFile (#71769)

Add a new API in SBTarget to Load Core from a SBFile.
This will enable a target to load core from a file descriptor.
So that in coredumper, we don't need to write core file to disk, instead
we can pass the input file descriptor to lldb directly.


Test:
```
(lldb) script
Python Interactive Interpreter. To exit, type 'quit()', 'exit()' or Ctrl-D.
>>> file_object = open("/home/hyubo/210hda79ms32sr0h", "r")
>>> fd=file_object.fileno()
>>> file = lldb.SBFile(fd,'r', True)
>>> error = lldb.SBError()
>>> target = lldb.debugger.CreateTarget(None)
>>> target.LoadCore(file,error)
SBProcess: pid = 56415, state = stopped, threads = 1
```