patch_all() is unsafe

[IlyaSukhanov]

There is a bit of ambiguity of patch_all() approach on aws-xray-sdk-python. Use thereof automatically enables new patchers regardless to how well they've been tested against real use cases (#48, #90). This in turn can can lead to a nasty surprise where deployment of lambda function will not work as it patches the calls.

Some ideas on making the situation better:

1. Discourage use of patch_all()due to its unsafe nature.
2. Do not include new patchers in patch_all() outside of major versions
3. Split patch_all() into two functions patch_all() and patch_all_bleeding_edge() where new, and un-vetted patchers are first introduced into patch_all_bleeding_edge() and after they've been tested are then introduced to patch_all()

[haotianw465]

Thank you for your feedback. These suggestions are very valuable for improving the SDK quality. We will update our documentation library patching section to properly explain the best practices. It's also reasonable to not include newly merged library support to patch_all() list as each library support has various use cases and implicit patching is surprising. We will look into better APIs for patching and post updates here.