feat(library/simplifier): bottom-up simplifier skeleton

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(library/simplifier): add rewrite_rule_set

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(library/simplifier): add rewrite_rule_set extension for managing rewrite rules in an environment

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