improve RPC error message "Invalid Transaction"

[brenzi]

Currently, extrinsics either get finalized or they fail with "Invalid Transaction".

I suggest that the developer can access more verbose error messages like

• extrinsic decoding failed
• signature verification failed
• wrong nonce
• not enough funds to pay fees
• module-specific failures
  • no such module
  • no such method

I could live with trace messages in the node log, but nicer would be to return these via RPC response

[xlc]

Related (maybe duplicated): #2246

[brenzi]

defenately related, but my requirement is a bit more relaxed, as node log would be sufficient for me.

[tomusdrw]

Already addressed by #3433. Logs can be displayed with -ltxpool=trace