Fixes

[chcmedeiros]

• fixes on the convert checks
• improving rs lib
• add shielded hash verification for maspTx and Ibc
  closes Incorrect spend authorization signatures returned by hardware wallet #70 Missing handling for dummy output notes #72 Calling NamadaApp::sign after NamadaApp::get_signature yields 0: Ledger | App Error: | 27012 apdu parameters invalid #74 NamadaApp::sign_masp_spends sometimes returns Ledger | App Error: | 28417 apdu sign verify error #76 Calling NamadaApp::sign in new session returns Ledger | App Error: | 27012 apdu parameters invalid #78 Ledger | App Error: | 28417 apdu sign verify error #66

[emmanuelm41]

Just left a few comments. I did my best to review the code using the knowledge I have about namada. Just wonder if it is correct the zemu snapshots are so different.