CXXCBC-615: Expose insert_raw & replace_raw in core txns attempt ctx

[DemetrisChr]

• Expose insert_raw and replace_raw in the core txns attempt context APIs, which have now been renamed to insert and replace.
• Remove the variants of insert and replace that use transcoders from the core API, as well as the overloads of core::transactions::transaction_get_result::content() that use transcoders
  • The C++ Public API, as well as the wrappers, have their own transcoder support, which makes these redundant.

[thejcfactor]

LGTM 👍

Also tested w/ the PYCBC-1595 changes. Thanks for making the updates!