High outliers for some REST API responses

Based on the metrics, it looks like some REST API responses have pretty high outliers while the average responses times are quite low.

## Requests pulling data from network

Might be related to the API pulling (or pushing) data from the network

### [getPeers](https://github.com/ChainSafe/lodestar/blob/05fe0ac00d9de61dc6e85225ef2d1c5e27ab714d/packages/beacon-node/src/api/impl/node/index.ts#L25)

_(needs more buckets between 100ms-1s)_


### [prepareBeaconCommitteeSubnet](https://github.com/ChainSafe/lodestar/blob/05fe0ac00d9de61dc6e85225ef2d1c5e27ab714d/packages/beacon-node/src/api/impl/validator/index.ts#L1200)

_(needs more buckets between 100ms-1s)_


## Requests pulling data from state

While other APIs that involve just pulling data from head state don't have this issue

### [getStateFinalityCheckpoints](https://github.com/ChainSafe/lodestar/blob/05fe0ac00d9de61dc6e85225ef2d1c5e27ab714d/packages/beacon-node/src/api/impl/beacon/state/index.ts#L70)


### [getStateValidators](https://github.com/ChainSafe/lodestar/blob/05fe0ac00d9de61dc6e85225ef2d1c5e27ab714d/packages/beacon-node/src/api/impl/beacon/state/index.ts#L83)

_(querying for low validator count)_


Start by inspecting the linked implementations in packages/beacon-node/src/api/impl/node/index.ts at getPeers, packages/beacon-node/src/api/impl/validator/index.ts at prepareBeaconCommitteeSubnet, and the state API entries in packages/beacon-node/src/api/impl/beacon/state/index.ts. Compare their response-time metrics and bucket coverage, then verify that the high outliers are explained or corrected and that the resulting distributions are observable.

Written by the indexing model from the issue text.