[Bug] Failed query is not logged

Bug report

For some failed queries, graph-node fails silently, not logging any error.

Ex.:
`http post http://localhost:8080/subgraphs/id/QmQohvyxLZLpwouzPF61kTzmLjgawmt6qDWZrPndz1M9EQ query='query MyQuery { _meta { block { number } } }'`
would return
`{
    "errors": [
        {
            "message": "Store error: database unavailable"
        }
    ]
}
`
but there are no indication of an error related to this query in the graph-node logs, making
the detection of the error very difficult on a sharded production environment.

`graph-node v0.29.0`

Relevant log output

no log output

IPFS hash

No response

Subgraph name or link to explorer

No response

Some information to help us out

• Tick this box if this bug is caused by a regression found in the latest release.
• Tick this box if this bug is specific to the hosted service.
• I have searched the issue tracker to make sure this issue is not a duplicate.

OS information

None

Start by reproducing the failed _meta query against graph-node and tracing how its GraphQL errors are handled and logged. The issue names no source files or tests; done means a failed query produces a useful error entry in the graph-node logs while still returning the reported response.