refactor: renames AssemblyLevelTest to AssemblyTest.
refactor: renames AssemblyFixtureConfigAttribute to

AssemblyFixtureCustomizationAttribute.
refactor: introduces StaticFactAttribute.
dev: makes NullGuardClauseAssertion ignore abstract methods.
dev: makes NullGuardClauseAssertion ignore abstract properties.
refactor: makes NullGuardClauseAssertion inherit from

IdiomaticMemberAssertion.
build: makes test projects treat compile warning as error on the

realse mode.
dev: addresses abstract and static issues in

MemberInitializationAssertion.
dev: addresses abstract and static issues in

ObjectDisposalAssertion.
refactor: moves out test types from Assertions namespace.
docs: adds release note for v0.22.1.
refactor: moves out PropertyExtensions from Assertions namespace.
dev: addresses get or set property issues in

MemberInitializationAssertion.
dev: adds tests for get or set property issues of

NullGuardClauseAssertion.
docs: adds or modifies release note for v0.22.1.
dev: implements IdiomaticAssertion.
refactor: uses IdiomaticAssertion as base classes of idiomatic

assertions.
docs: adds release note for v0.22.1.
build: increment patch version,

to indicate that this fixes that idiomatic assertions throws when
verifying irrelevant members.