RCORE-2257 Remove unneeded evergreen tasks/build variants

[jbreams]

What, How & Why?

Removes a bunch of evergreen tasks that are no longer relevant after the deprecation.

• Benchmarks
• Sync corpus testing
• Unused network faultyness testing (toxiproxy)
• MacOS 11 builders
• All the evg config for launching baas on evg-managed remote hosts
• libfuzzer fuzzer task/artifacts

☑️ 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 jonathan.reams_3420

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 114 unchanged lines in 10 files lost coverage.
• Overall coverage decreased (-0.02%) to 91.103%

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Files with Coverage Reduction	New Missed Lines	%
src/realm/util/serializer.cpp	1	90.43%
src/realm/object-store/shared_realm.cpp	2	91.9%
src/realm/unicode.cpp	3	83.83%
test/test_thread.cpp	3	66.14%
src/realm/bplustree.cpp	6	72.55%
src/realm/sync/noinst/client_impl_base.cpp	6	82.72%
src/realm/sync/instruction_applier.cpp	7	68.01%
src/realm/sync/network/network.hpp	7	85.28%
src/realm/sync/noinst/server/server.cpp	20	73.95%
test/fuzz_group.cpp	59	46.41%

Totals
Change from base Build 2607:	-0.02%
Covered Lines:	217173
Relevant Lines:	238382

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💛 - Coveralls