add monero_wallet integration tests

[fxrstor]

related to issue #800

• covers the required test scope
• renames monero-wallet crate to monero_wallet because apparently there's a name conflict which prevents the tests from running with default parameters.
• introduces an integration_test macro. inline async closures can keep captured wallet resources alive past the test body, which can race with harness teardown and trigger a segfault during c++ wallet destruction. the macro moves test logic into a separate async function passed to setup_test which gives wallet resources a clearer drop boundary before teardown.

test results (i3-4160):