erasure-code: move to ErasureCode::to_{int,bool}

erasure-code: move to ErasureCode::to_{int,bool}

The parameter parser helpers to_int and to_bool are moved from
ErasureCode{Jerasure,Isa} to ErasureCode.

The prototype is modified to return a status instead of the value. An
error ostream is provided as the last argument because ErasureCode
cannot use dout() or derr().

http://tracker.ceph.com/issues/8496 Refs: #8496

Signed-off-by: Loic Dachary <loic@dachary.org>