Create symbols with Symbol.for() (#5131)

* Create symbols with Symbol.for()

When multiple copies of `@graphql-tools/delegate` are available in a workspace (eg: because `stitch` and `wrap` depend on different versions), creating symbols with `Symbol()` can lead to bugs when one version of `delegate` sets an object property using its version of the symbol which the other `delegate` instance will not be able to access. Using `Symbol.for()` fixes this: as long as both versions of delegate use the same string description, they will refer to the same symbol.

* Add changeset

.changeset/bright-glasses-watch.md

@@ -0,0 +1,5 @@
+---
+'@graphql-tools/delegate': patch
+---
+
+Create symbols with Symbol.for() because multiple copies of delegate cause stitching bugs otherwise.

packages/delegate/src/symbols.ts

@@ -1,3 +1,3 @@
-export const UNPATHED_ERRORS_SYMBOL = Symbol('subschemaErrors');
-export const OBJECT_SUBSCHEMA_SYMBOL = Symbol('initialSubschema');
-export const FIELD_SUBSCHEMA_MAP_SYMBOL = Symbol('subschemaMap');
+export const UNPATHED_ERRORS_SYMBOL = Symbol.for('subschemaErrors');
+export const OBJECT_SUBSCHEMA_SYMBOL = Symbol.for('initialSubschema');
+export const FIELD_SUBSCHEMA_MAP_SYMBOL = Symbol.for('subschemaMap');