Backport from Core's PR10997 and PR11125
PR10997:
```
79191f5 Add option -stdinrpcpass to allow RPC password to be read from standa…
```
and the tests for it:
PR11125:
```
29e1dfb [test] Add bitcoin-cli -stdin and -stdinrpcpass functional tests (João Barbosa)
ce379b4 [test] Replace check_output with low level version (João Barbosa)
232e3e8 [test] Add assert_raises_process_error to assert process errors (João Barbosa)
5c18a84 [test] Add support for custom arguments to TestNodeCLI (João Barbosa)
e127494 [test] Improve assert_raises_jsonrpc docstring (João Barbosa)
7696841 Fix style in -stdin and -stdinrpcpass handling (João Barbosa)
```