feat: Improve withdraw-all-rewards UX (backport cosmos#9781) (cosmos#…

…9825)

* feat: Improve withdraw-all-rewards UX (cosmos#9781)

## Description
Related to cosmos#9489, this PR improves the UX when using the `withdraw-all-rewards` command by forcing the broadcast mode to `block` if the chunk size is greater than 0. This will ensure that the transactions do not fail even if the user uses invalid broadcast modes for this command (`sync` and `async`).

---

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- [ ] added `!` to the type prefix if API or client breaking change
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(cherry picked from commit 90157fc)

# Conflicts:
#	CHANGELOG.md

* Update CHANGELOG.md

Co-authored-by: Riccardo Montagnin <riccardo.montagnin@gmail.com>
Co-authored-by: Robert Zaremba <robert@zaremba.ch>

CHANGELOG.md

@@ -36,6 +36,10 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ## Unreleased
 
+### Client Breaking Changes
+
+* [\#9781](https://github.com/cosmos/cosmos-sdk/pull/9781) Improve`withdraw-all-rewards` UX when broadcast mode `async` or `async` is used.
+
 ## [v0.42.8](https://github.com/cosmos/cosmos-sdk/releases/tag/v0.42.8) - 2021-07-30
 
 ### Features