Overflow/underflow check for -maxsendbuffer and -maxreceivebuffer

[JackPiri]

Handling cases like -maxsendbuffer=-1, -maxsendbuffer=0, -maxsendbuffer=4294967296, etc...

[a-petrini]

Looks good, thanks!

[ptagl]

Thanks for the effort in improving checks on input parameters!

To me, the changes seem in line with the typical approach used in that file, I was wondering if we could start thinking of a new approach to separate parameters validation from usage.

In particular, I wonder if we could introduce a new function like ValidateStartupArguments() that takes care of performing all the sanity checks on the inputs while keeping AppInit2() lite and more readable.

Given that we may be using similar validations for several arguments in the future, we may also think of including a second util function like ValidateRanges(argKey, [optional] min, [option] max) to reduce code duplication.

In such a way, we could probably also easily increase code coverage with some unit tests.

What do you think?

[drgora]

Thank you for the PR! I left a small comment that I believe should be addressed before merging.
I also second @ptagl on his comment on modularization.

[titusen]

I agree with Paolos comments. The rest LGTM, thanks.

[drgora]

This PR looks good to me. I left a couple small comments that I believe might be good addressing before merge, but not blocking. Thank you.