mergeSchemas: extractedResolvers are overwritten by default resolvers from schema

[mattkrick]

Describe the bug

In mergeSchemas, the resolvers passed in via the resolvers argument should overwrite any resolvers coming from the schemas.

To Reproduce
Steps to reproduce the behavior:

const mySchema = mergeSchemas(...) // this will add a default resolver to every field
const withNestedSchema = mergeSchemas({
  schemas: [mySchema],
  resolvers: {_extQuery: { projects: () => 42}} // this resolver gets overwritten during merge!
})

Expected behavior

The custom resolvers I pass in are the ones that are used.
Simplest solution is to just add the custom resolvers to the end of the array before merging.

master...mattkrick:patch-1#diff-a47be556064f0c5e1d5cd8d16ee14fc36b8f15b5d53f9aecbe5cebf5f1bb3b6aL22-R34

[mattkrick]

ack! sorry for ghosting this issue.
thanks for getting this across the line!
fixed in #4463