Get blob fulu (#15610)

* wip

* wip

* adding ssz marshalling

* updating function for readability

* adding unit tests and fixing ssz

* gaz

* linting

* fixing test

* wip

* fixing mock blocker

* fixing test

* fixing tests and handler

* updating unit test for more coverage

* adding some comments

* self review

* gofmt

* updating and consolidating tests

* moving functional options so it can be used properly

* gofmt

* more missed gofmt

* Update beacon-chain/rpc/endpoints.go

Co-authored-by: Radosław Kapka <rkapka@wp.pl>

* Update beacon-chain/rpc/lookup/blocker.go

Co-authored-by: Radosław Kapka <rkapka@wp.pl>

* Update beacon-chain/rpc/eth/beacon/handlers.go

Co-authored-by: Radosław Kapka <rkapka@wp.pl>

* radek feedback

* fixing tests

* fixing test

* moving endpoint in test

* removed unneeded comment

* fixing linting from latest develop merge

* fixing linting from latest develop merge

* Update beacon-chain/rpc/eth/blob/handlers.go

Co-authored-by: Radosław Kapka <rkapka@wp.pl>

* Update beacon-chain/rpc/eth/blob/handlers.go

Co-authored-by: Radosław Kapka <rkapka@wp.pl>

* reverting change

* reverting change

* adding in better error for which hashes are missing

* Update beacon-chain/rpc/lookup/blocker.go

Co-authored-by: Radosław Kapka <rkapka@wp.pl>

* fixing unit test

* gofmt

---------

Co-authored-by: Radosław Kapka <rkapka@wp.pl>

api/server/structs/endpoints_beacon.go

@@ -290,3 +290,9 @@ type GetProposerLookaheadResponse struct {
 	Finalized           bool     `json:"finalized"`
 	Data                []string `json:"data"` // validator indexes
 }
+
+type GetBlobsResponse struct {
+	ExecutionOptimistic bool     `json:"execution_optimistic"`
+	Finalized           bool     `json:"finalized"`
+	Data                []string `json:"data"` //blobs
+}