Pass plugin_name in SBProcess::SaveCore

This CL allows to use minidump save-core functionality (https://reviews.llvm.org/D108233) via SBProcess interface.
After adding a support from gdb-remote client (https://reviews.llvm.org/D101329) if the plugin name is empty the plugin manager will try to save the core directly from the process plugin.
See https://github.com/llvm/llvm-project/blob/main/lldb/source/Core/PluginManager.cpp#L696

To have an ability to save the core with minidump plugin I added plugin name as a parameter in SBProcess::SaveCore.

Reviewed By: clayborg

Differential Revision: https://reviews.llvm.org/D125325