Merge branch 'adrian/light-sdk' (#2220)

* origin/adrian/light-sdk:
  Adds a method to serialize transactions
  Makes internal struct of `RevealPk` private
  Fixes datetime
  Splits light sdk queries into multiple files
  Renames light sdk crate and adds description
  Adds missing feature for tendermint-rpc in light sdk
  Changelog #2220
  Imports `HttpClient` from `tendermint_rpc`
  Updates types and imports after rebase
  Updates docstrings and fixes clippy
  Some small type simplifications in the reading api
  [feat]: Added rpc functions to light sdk
  Renames `get_msg_to_sign` to `get_sign_bytes`
  [feat]: Small fixes and making stuff public
  First draft of all transactions in light sdk
  Refactors pos txs in separate file. Improved shared functions
  Created light SDK builders.
  First attempt at overview of light-sdk

.changelog/unreleased/SDK/2220-light-sdk.md

@@ -0,0 +1 @@
+- Added light sdk ([\#2220](https://github.com/anoma/namada/pull/2220))