fix: let clang-tidy allow bool conversions in conditions (#235)

* fix: let clang-tidy allow bool conversions in conditions

See googleapis/google-cloud-cpp-spanner#1377 for rationale.

Author: devjgm

.clang-tidy

@@ -73,3 +73,5 @@ CheckOptions:
   - { key: readability-identifier-naming.MemberConstantPrefix,     value: k         }
   - { key: readability-identifier-naming.StaticConstantCase,       value: CamelCase }
   - { key: readability-identifier-naming.StaticConstantPrefix,     value: k         }
+  - { key: readability-implicit-bool-conversion.AllowIntegerConditions,  value: 1   }
+  - { key: readability-implicit-bool-conversion.AllowPointerConditions,  value: 1   }