fix(fragment): merge the nested fragments fields (#8075)

[dshekhar95]

cherry-pick from #8075

Fixes https://discuss.dgraph.io/t/graphql-field-collection-does-not-work-with-dgraph/15646

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[dshekhar95]

Have tested locally, fix works. Need to add unit test case still

[coveralls]

Coverage increased (+0.01%) to 37.195% when pulling bd797b9 on dshekhar95-cherry-pick-8075 into bc5f584 on main.

[MichelDiz]

@dshekhar95 Do you have a test proof? that I can run in my end. Looks like you have fixed and send it to the user PoolShark correct? So his example could be a test.

BTW, can you sign the CLA?

[matthewmcneely]

This one definitely needs tests.

[dshekhar95]

@dshekhar95 Do you have a test proof? that I can run in my end. Looks like you have fixed and send it to the user PoolShark correct? So his example could be a test.

BTW, can you sign the CLA?

[meghalims]

LGTM. Thanks for adding test. Please go ahead and merge it

[damonfeldman]

Note this fixes a bug where a fragment is used in a query but data is not returned as required by the GraphQL spec. (See discuss link above for details)