RCORE-2180 Add basic translation of NSExceptions to Status

[tgoyne]

When the Swift API is misused from within a callback from core a NSException may escape, which we want to propagate. Since this is always a fatal error that cannot be programmatically handled by the user, we can always translate this to UnknownError rather than trying to preserve the original error code.

Fixes #7836.

[coveralls-official]

Pull Request Test Coverage Report for Build thomas.goyne_495

Details

• 26 of 27 (96.3%) changed or added relevant lines in 2 files are covered.
• 65 unchanged lines in 19 files lost coverage.
• Overall coverage decreased (-0.003%) to 91.114%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/realm/exceptions.mm	16	17	94.12%

Files with Coverage Reduction	New Missed Lines	%
src/realm/array_backlink.cpp	1	91.38%
src/realm/dictionary.cpp	1	85.16%
src/realm/sort_descriptor.cpp	1	94.06%
src/realm/util/file.cpp	1	84.84%
src/realm/util/serializer.cpp	1	90.43%
test/test_dictionary.cpp	1	99.83%
src/realm/query_expression.hpp	2	93.81%
src/realm/table_view.cpp	2	92.99%
src/realm/sync/client.cpp	3	90.96%
src/realm/sync/noinst/protocol_codec.hpp	3	75.74%

Totals
Change from base Build 2589:	-0.003%
Covered Lines:	217379
Relevant Lines:	238580

---

💛 - Coveralls