Scalability and Code readability

[shivangvijay]

https://github.com/scpeters/benchmark/blob/74fb82c80a60a1c5cade28bc16c874c05cb737b8/gtest/include/gtest/gtest-param-test.h#L1287C1-L1296C2

https://github.com/scpeters/benchmark/blame/74fb82c80a60a1c5cade28bc16c874c05cb737b8/gtest/include/gtest/internal/gtest-param-util-generated.h#L4969-L5025

@mabelzhang @scpeters Is there any particular reason why variadic templates are not being used? Currently, we are limited to using 10 parameters. However, if these were replaced by variadic templates, both code readability and scalability would improve.