feat(samples): adds read and filter snippets (#586)

* Reads and filters WIP, working Reads tests and current format for Reads snippets

* working tests for solo filters

* Composing filters

* add bulk region tags

* Change testing instance

* Linted

* feat: implement instance and table level IAM policy (#584)

* feat: add table level IAM policy controls

* lint: lint

* feat: add instance level IAM policy

* docs: update description

* docs: add document snippets

* lint: lint

* Linted
Fixed headers
Removed unnceccessary asyncs
Arrow functions where possible

* Arrow functions

* destructure Bigtable require

* Using snapshots for testing

* Change functions to use a switch

* Fix timezone issue for tests

* Lint snapshot files

* Clean up loops, add update snapshot method