fix duplicated shadow dom (#1095)

* fix: duplicated elements in shadow doms

clean observers before taking new full snapshots

* add checker for replayer to make it stable when data has duplicated nodes

* apply review suggestions

* add change log

* Apply formatting changes

* update prettier to fit the master branch

---------

Co-authored-by: Mark-Fenng <Mark-Fenng@users.noreply.github.com>

yarn.lock

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-
-prettier@^2.7.1:
+prettier@2.8.4, prettier@^2.7.1:
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