fix(kernel/metavar): make sure the justification and substitution are always matching each other

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
style(kernel/metavar): add missing includes

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(library/elaborator): add missing conflict justification

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>