Breaking changes in v3.0.0

[Michael Diamant]

Itemizes functionality that will be removed in the upcoming major release.

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Migrating a few thoughts from v2.0.0. If we'd like to pursue, we can add stories.

• Modify transaction construction to use builders (or similar) in order to minimize backwards incompatible changes.
  • Related: https://algorand.atlassian.net/wiki/spaces/FDE/pages/491716666/SuggestedParams+Thoughts#Go
• Remove special cases from HTTP Clients:
  • Update generator templates to remove special cases.
  • Regenerate client libraries.
• Split algod and indexer generated types: algorand/generator#59