[#1] Add Span implementation from Zserio C++ runtime

runtime/ClangTidySuppressions.txt

@@ -1,2 +1,31 @@
+# This is necessary for low level implementation of Span to mimic standard C++20 'std::span' abstraction.
+cppcoreguidelines-avoid-c-arrays:src/zserio/Span.h:112
+cppcoreguidelines-avoid-c-arrays:src/zserio/Span.h:123
+cppcoreguidelines-avoid-c-arrays:src/zserio/Span.h:136
+cppcoreguidelines-avoid-c-arrays:src/zserio/Span.h:148
+cppcoreguidelines-avoid-c-arrays:src/zserio/Span.h:161
+cppcoreguidelines-avoid-c-arrays:src/zserio/Span.h:174
+
+# This is necessary for low level implementation of Span to mimic standard C++20 'std::span' abstraction.
+cppcoreguidelines-pro-bounds-array-to-pointer-decay:src/zserio/Span.h:113
+
+# This is necessary for low level implementation of Span to mimic standard C++20 'std::span' abstraction.
+google-explicit-constructor:src/zserio/Span.h:112
+google-explicit-constructor:src/zserio/Span.h:125
+google-explicit-constructor:src/zserio/Span.h:138
+google-explicit-constructor:src/zserio/Span.h:150
+google-explicit-constructor:src/zserio/Span.h:163
+google-explicit-constructor:src/zserio/Span.h:176
+
+# False positive, this is a template method.
+modernize-use-equals-default:src/zserio/Span.h:80
+
 # Intentional tests.
 google-explicit-constructor:test/zserio/BuiltInOperatorsTest.cpp:25
+
+# Intentional tests.
+cppcoreguidelines-avoid-c-arrays:test/zserio/SpanTest.cpp:45
+
+# Intentional tests.
+cppcoreguidelines-pro-bounds-pointer-arithmetic:test/zserio/SpanTest.cpp:34
+cppcoreguidelines-pro-bounds-pointer-arithmetic:test/zserio/SpanTest.cpp:38

runtime/src/CMakeLists.txt

@@ -21,6 +21,7 @@ set(ZSERIO_CPP17_RUNTIME_LIB_SRCS
     zserio/BuiltInOperators.cpp
     zserio/BuiltInOperators.h
     zserio/CppRuntimeVersion.h
+    zserio/Span.h
     zserio/Types.h
 )