(WifiS3 WiFiClient) Reduce memory allocations

Embedded devices should avoid to use memory allocation - or limit allocations to minimum. Unfortunately, the code for WiFi does not honour this rule.

- don't use std::string, use static allocated buffer
- don't use std::make_shared - we have C++17, implementing copy constructors for every class is no longer required. WiFiClient can have preallocated buffer as member variable. The programmer can possibly choose to use std::make_shared for the whole WiFIClient instance, if it needs to share it by other objects.
- typo: destroy_at_distructor
- bug: the flag destroy_at_distructor is never used, destructor is empty.

https://github.com/arduino/ArduinoCore-renesas/blob/03b4a91db49dae7601701c33cd09924ea6b363d3/libraries/WiFiS3/src/WiFiClient.cpp#L6

Start with libraries/WiFiS3/src/WiFiClient.cpp at the linked allocation code. Review how WiFiClient currently uses std::string, std::make_shared, and the destroy_at_distructor flag. Done means reducing avoidable allocations, correcting the typo, and making the destruction flag meaningful rather than leaving the destructor empty.

Written by the indexing model from the issue text.