Refactor {Module,Submodule}EffectiveStatementImpl

Refactor {Module,Submodule}EffectiveStatementImpl

Modules and submodules are tied together via AbstractEffectiveModule,
which holds on to old layout. While it is not directly harmful to
these implementations, having statement creation outside of actual
constructors is a long-term goal.

Refactor AbstractEffectiveModule and thus both implementations to
create substatements separately in BaseStatementSupport.

The inlining of submodule statements is hooked into
BaseStatementSupport lifecycle via buildEffectiveSubstatements(),
so that modules can stop mucking with statement build rules and just
pick up whatever was created for the corresponding submodule.

For declared statements we introduce AbstractDeclaredEffectiveRootStatement
as a replacement for AbstractRootStatement, which is now deprecated
for removal.

JIRA: YANGTOOLS-1065
Change-Id: I032bb1ea4f2ee5db87d9b0dbbdeb89f152bc4593
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>