refactor: move simapp.App to runtime.AppI

[julienrbrt]

Description

Move simapp.App to runtime.AppI, as chains should not import simapp anymore.
ref: #13376 (comment)

---

Author Checklist

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I have...

• included the correct type prefix in the PR title
• added ! to the type prefix if API or client breaking change
• targeted the correct branch (see PR Targeting)
• provided a link to the relevant issue or specification
• followed the guidelines for building modules
• included the necessary unit and integration tests
• added a changelog entry to CHANGELOG.md
• included comments for documenting Go code
• updated the relevant documentation or specification
• reviewed "Files changed" and left comments if necessary
• confirmed all CI checks have passed

Reviewers Checklist

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your handle next to the items reviewed if you only reviewed selected items.

I have...

• confirmed the correct type prefix in the PR title
• confirmed ! in the type prefix if API or client breaking change
• confirmed all author checklist items have been addressed
• reviewed state machine logic
• reviewed API design and naming
• reviewed documentation is accurate
• reviewed tests and test coverage
• manually tested (if applicable)

[codecov]

Codecov Report

Merging #13378 (fa4d1ba) into main (af81605) will decrease coverage by 1.98%.
The diff coverage is 0.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #13378      +/-   ##
==========================================
- Coverage   56.12%   54.14%   -1.99%     
==========================================
  Files         713      651      -62     
  Lines       60174    56055    -4119     
==========================================
- Hits        33774    30349    -3425     
+ Misses      23642    23281     -361     
+ Partials     2758     2425     -333     

Impacted Files	Coverage Δ
simapp/app.go	77.30% <ø> (ø)
simapp/utils.go	21.91% <0.00%> (ø)
x/staking/simulation/operations.go	74.54% <0.00%> (-1.38%)	⬇️
tx/textual/valuerenderer/valuerenderer.go
orm/encoding/ormfield/codec.go
orm/model/ormtable/singleton.go
orm/model/ormdb/json.go
depinject/module_key.go
depinject/internal/codegen/file.go
orm/model/ormtable/auto_increment.go
... and 79 more

[tac0turtle]

can we get an entry in upgrading.md

[julienrbrt]

can we get an entry in upgrading.md

Sure thing, added!