feat: deeper fragment merging

[benjie]

Follow up to #1542; this passes the schema through to mergeAST so that the query can be further simplified in a type-aware way (i.e. spreading a fragment of type Test inside a scope that can only be type Test will result in the fragment being fully inlined).

Given this query:

{ test { id ...T } } fragment T on Test { isTest }

Pressing "Merge" previously simplified to:

{ test { id ... on Test { isTest } } }

But with this change, it now simplifies to:

{ test { id isTest } }

[codecov]

Codecov Report

Merging #1703 into main will not change coverage.
The diff coverage is 0.00%.

@@ Coverage Diff @@ ## main #1703 +/- ## ======================================= Coverage 63.81% 63.81% ======================================= Files 86 86 Lines 4692 4692 Branches 1256 1256 ======================================= Hits 2994 2994 Misses 1440 1440 Partials 258 258 

Impacted Files	Coverage Δ
packages/graphiql/src/components/GraphiQL.tsx	59.89% <0.00%> (ø)

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[acao]

thank you @benjie !