Change to case insensitive header lookup

[vtipparam]

Setting the header Apollo-Query-Plan-Experimental has no effect. Setting the request header Apollo-Query-Plan-Experimental is expected to populate the query plan in the response but it does not. We are performing case sensitive lookup on the headers. See #2337 for details.

Adding expressMiddleware handler particularly exposes the issue. Will add a separate PR to address the expressMiddleware issue.

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🦋 Changeset detected

Latest commit: 22c9a36

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 7 packages

Name	Type
@apollo/gateway	Patch
@apollo/federation-internals	Patch
@apollo/composition	Patch
@apollo/query-planner	Patch
@apollo/query-graphs	Patch
@apollo/subgraph	Patch
apollo-federation-integration-testsuite	Patch

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[trevor-scheer]

This shouldn't be necessary, the headers object in question here is:
/~https://github.com/apollographql/apollo-server/blob/c835637be07929e3bebe8f3b262588c6d918e694/packages/server/src/utils/makeGatewayGraphQLRequestContext.ts#L163-L164 (which uses the case-insensitive HeaderMap internally).

This should no longer be an issue via apollographql/apollo-server#7313