Fix combination runner/converter, Expecto directory verification, and…

[SimonCropp]

… clipboard accept

• CombinationRunner: validate every input list is non-empty in the constructor with a descriptive message instead of a raw IndexOutOfRangeException
• CombinationRunner: pass the raw method result to after-callbacks; only the serialized CombinationResult is wrapped in InfoBuilder when recording is active
• CombinationResultsConverter: cache GetNameForParameter per distinct key value instead of recomputing it for every cell (O(distinct) instead of O(rows*keys))
• Verify.Expecto: the VerifyDirectory(DirectoryInfo) overloads now capture GetCallingAssembly and call the core directly, so the caller's assembly is used rather than Verify.Expecto
• Verify.Expecto: use ExceptionDispatchInfo to rethrow the inner exception so the original stack trace is preserved
• ClipboardAccept: parse Verify_DisableClipboard leniently (1/0/yes/no/on/off/ true/false) and warn instead of throwing from the static constructor, which poisoned the type with a TypeInitializationException
• ClipboardAccept: shell-escape substituted paths so metacharacters ($, `) in a path are not expanded
• Add tests for the above