Replace ObjKey with RowKey in selected places

[jedelbo]

What, How & Why?

This will prevent us from accidently creating an ObjKey from something that cannot identify an Obj.

☑️ ToDos

• 📝 Changelog update
• 🚦 Tests (or not relevant)
• C-API, if public C++ API changed
• bindgen/spec.yml, if public C++ API changed

[coveralls-official]

Pull Request Test Coverage Report for Build jorgen.edelbo_330

Details

• 62 of 64 (96.88%) changed or added relevant lines in 7 files are covered.
• 61 unchanged lines in 10 files lost coverage.
• Overall coverage increased (+0.03%) to 91.032%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/realm/cluster.cpp	25	26	96.15%
src/realm/cluster_tree.hpp	1	2	50.0%

Files with Coverage Reduction	New Missed Lines	%
src/realm/query_engine.hpp	1	94.15%
src/realm/sort_descriptor.cpp	1	94.06%
src/realm/sync/noinst/server/server_history.cpp	1	63.7%
src/realm/query_expression.hpp	2	93.85%
src/realm/sync/network/http.hpp	2	82.27%
src/realm/mixed.cpp	3	86.46%
src/realm/table.cpp	4	90.42%
src/realm/sync/noinst/client_impl_base.cpp	7	82.36%
src/realm/sync/noinst/server/server.cpp	14	73.67%
test/fuzz_group.cpp	26	48.33%

Totals
Change from base Build james.stone_566:	0.03%
Covered Lines:	215433
Relevant Lines:	236657

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💛 - Coveralls

[ironage]

Great idea, type safety is our friend.