added sealed operator

[cowboyphilosopher]

added new operator sealed. format: (sealed (Expression with sealed variable list) (Term with variables to seal)) example: (sealed ($x $y) (= ($x $y) ($a $b)) $x and $y should be replaced with new unique variables in the Term value this new version uses UUID values to make them more explicitly unique rather than the ReplacingMapper

[vsbogd]

@cowboyphilosopher, question to the previous PR https://github.com/trueagi-io/hyperon-experimental/pull/392#pullrequestreview-1573961189 is still valid. In practice every query to the atomspace replaces variables in returned atoms, thus effectively sealed doesn't add any value.

[vsbogd]

Replaced by #609