Improve speculative shielded ctx (backport #4019)

[mergify]

Describe your changes

Closes #3457.
Closes #2593.

Moved the transition to the SpeculativeContext from the SDK to the client to have access to the (possible) tx result. The transition is now performed when:

• the submitted transaction is successfully applied
• the transaction is broadcasted
• the transaction is dumped to storage

The transition is not performed when:

• the transaction gets dry-run
• the transaction is loaded from storage

Added an integration test to verify the behavior of the client when in a speculative context.

Checklist before merging

• If this PR has some consensus breaking changes, I added the corresponding breaking:: labels
  • This will require 2 reviewers to approve the changes
• If this PR requires changes to the docs or specs, a corresponding PR is opened in the namada-docs repo
  • Relevant PR if applies:
• If this PR affects services such as namada-indexer or namada-masp-indexer, a corresponding PR is opened in that repo
  • Relevant PR if applies:

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This is an automatic backport of pull request #4019 done by [Mergify](https://mergify.com).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.05%. Comparing base (f1503cc) to head (4e02b54).
Report is 8 commits behind head on maint-0.45.

Additional details and impacted files

@@              Coverage Diff               @@
##           maint-0.45    #4070      +/-   ##
==============================================
- Coverage       74.05%   74.05%   -0.01%     
==============================================
  Files             341      341              
  Lines          106581   106567      -14     
==============================================
- Hits            78927    78913      -14     
  Misses          27654    27654              

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