[lldb/interpreter] Improve REPL init file compatibility
This patch changes the command interpreter sourcing logic for the REPL
init file. Instead of looking for a arbitrary file name, it standardizes
the REPL init file name to match to following scheme:
This will make the naming more homogenous and the sourcing logic future-proof.
Differential Revision: https://reviews.llvm.org/D86987
Signed-off-by: Med Ismail Bennani <email@example.com>