Remove OpenSSL dependency for Base64 encoding

[RickWinter]

A dependency on OpenSSL just for base64 encoding is excessive. Implement base64 encoding per RFC spec.

[Jinming-Hu]

Generating uuid also depends on OpenSSL. We cannot get rid of it anyway.

[ahsonkhan]

A relatively simple port of https://github.com/Azure/azure-sdk-for-c/blob/main/sdk/src/azure/core/az_base64.c should be sufficient here.