BUG-7052: Move qnameFromArgument to StmtContextUtils
This has no dependencies on RFC6020, move it to common statement
utilities. Also takes all utility methods used by it.
This removes {BuildGlobal,Substatement}Context->rfc6020.Utils and
rfc6020.Utils -> reactor.RootStatementContext dependencies, which
by defition is Good.
Change-Id: I9ff90a0be8c4eaee2c085c9333a71c12619d2d7c
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>
(cherry picked from commit
742be43770eb77e1898466d3d887422cc9127e40)