* Initialize fork graph in program cache during bank_forks creation
* rename BankForks::new to BankForks::new_rw_arc
* fix compilation
* no need to set fork_graph on insert()
* fix partition tests
This macro is used a lot for tests to create a ledger path in order to
open a Blockstore. Files will be left on disk unless the test remembers
to call Blockstore::destroy() on the directory. So, instead of requiring
this, use the get_tmp_ledger_path_auto_delete!() macro that creates a
TempDir (which automatically deletes itself when it goes out of scope).