Proposal for time series deletion with block storage (cortexproject#4274)

* Add proposal document

Signed-off-by: Gofman <ilang@147dda11e800.ant.amazon.com>
Signed-off-by: ilangofman <igofman99@gmail.com>

* Minor text modifications

Signed-off-by: ilangofman <igofman99@gmail.com>

* Implement requested changes to the proposal

Signed-off-by: ilangofman <igofman99@gmail.com>

* Fix mention of Compactor instead of purger in proposal

Signed-off-by: ilangofman <igofman99@gmail.com>

* Fixed wording and spelling in proposal

Signed-off-by: ilangofman <igofman99@gmail.com>

* Update the cache invalidation method

Signed-off-by: ilangofman <igofman99@gmail.com>

* Fix wording on cache invalidation section

Signed-off-by: ilangofman <igofman99@gmail.com>

* Minor wording additions

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* Remove white-noise from text

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* Remove the deleting state and change cache invalidation

Signed-off-by: ilangofman <igofman99@gmail.com>

* Add deleted state and update cache invalidation

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* Add one word to clear things up

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* update api limits section

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* ran clean white noise

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Author: ilangofman