[Tracking] - HTTP Endpoint Cleanup

[saolyn]

🦄 HTTP Endpoint Cleanup Tracking

Feature Description

Now that all the validator client endpoints have been modified to be HTTP endpoints we need to clean up a few things before moving on to converting the rest of the Beacon API.

Tasks

• Remove the validation package
• Change usages of s.V1Alpha1Server to use the core package instead
• Write documentation on how to add new custom endpoints
• Add a page with dedicated documentation for each endpoint
• Handle Cors on all endoints
• Support comma-separated query values in a more future-proof way than Support comma-separated query params in Beacon API #12966
• Remove validation package from beacon-chain/rpc/eth/shared/structs_blocks.go
• Move structs to a structs package and group them into definition-ToConsensus-FromConsensus for each type
• Decide whether FromConsensus functions should start with a nil check
• Decide on a common uint encoding pattern in FromConsensus functions. fmt.Sprintf is less verbose than strconv.
• Allow SSL
• Use DecodeHexWithLength in ToConsensus functions
• Use the exact param name inside handlers in calls to ValidateHex/ValidateUint
• Static analyzer checking that HandleError is always followed with return
• Versioning scheme for custom endpoints
• Rename http package to httputil to avoid aliasing in every handler file
• Use UintFromQuery instead of ValidateUint because it's strictly better (need to verify if that's the case first) and make the latter unimported. Would it make sense to create a HexFromQuery function?
• Add spans to Prysm endpoints
• Rename rpc/eth to api/beacon
• Rename Bls to BLS in field names

This issue should be closed after all of the above tasks are complete.

[rkapka]

Change s.V1Alpha1Server.GetBeaconBlock call in produceBlockV3 to use the core package instead

This one is implemented in #12927

[james-prysm]

we need to migrate lightclient to stop using the eth proto package and instead use just the v1alphav1

[james-prysm]

there are duplicate code in the builder types + how it uses ssz that could be cleaned up