This commit updates `VerifyOrQuit()` and `SuccessOrQuit()` macros to
include the failed condition in the error message that is printed on
a failure (in addition to function name and line number where the
error happened). This commit also changes the second parameter
(`aMessage`) to in these macros to be optional.
This commit also updates unit tests to remove the second `aMessage`
string in cases where the failure can be inferred from the condition
itself.
This commit adds a new class `HeapString` as heap allocated string.
The buffer to store the string is allocated from heap and is manged
by the `HeapString` class itself, e.g., it may be reused and/or freed
and reallocated when the string is set. The `HeapString` destructor
will always free the allocated buffer.
This commit also adds a unit test `test_heap_string` for the new
class.