Add RejectExtensionOptionsDecorator

[aaronc]

ref: #6213

This adds an AnteDecorator to reject all transactions with TxBody.extension_options set. Users who want to use extension options need to override this. For the SDK, the correct behavior is to reject.

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[codecov]

Codecov Report

Merging #6988 into master will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #6988      +/-   ##
==========================================
+ Coverage   54.79%   54.81%   +0.02%     
==========================================
  Files         541      542       +1     
  Lines       36889    36907      +18     
==========================================
+ Hits        20212    20230      +18     
  Misses      15021    15021              
  Partials     1656     1656              

[amaury1093]

LGTM, small comment on why we need a separate interface for extensions tx builders.