This removes all explicit mention of SCRIPT_DISALLOW_SEGWIT_RECOVERY from validation.cpp
Changes the current behavior by making it impossible to accept segwit recovery transactions
into the mempool, even with -acceptnonstdtxn=1 (this is the same as with all other
script verify flags that are included in standard flags).
Functional test is amended to reflect this change in behavior.
Depends on D3065