Remove `future` package

[Michael Diamant]

Problem

The story requests relocating files from https://github.com/algorand/go-algorand-sdk/tree/develop/future to the top-level + overwriting existing functionality.

Rationale taken from https://gist.github.com/algochoi/75e8158e588ae2620d77c4497ff436d5:

• The new Transaction format in the SDK encourages users to call the v2/params endpoint to populate the SuggestedParams (sp) object
• Biggest functional difference is that the old Transaction format does not support setting the minFee, and instead hardcodes a value based on v5 consensus parameters. The new format can set a minFee through the sp object.
  • Currently, the SDKs hardcode the minFee anyway (in both old and new txn formats) - probably because the network is never congested anyway, but should be updated.

For future extensions, we should consider a builder pattern or similar to make backwards compatibility easier.

Acceptance criteria:

• No future package exists + functionality moved to top-level dir.
• https://github.com/algorand/docs + developer portal updates ready to be merged

Solution

Dependencies

Urgency