Refactor middleware tests out of baseapp_test

[amaury1093]

Part of the tx working group

Summary

Fix technical debt in tests after the baseapp middleware refactor (#9996).

ref: #10028 (comment), #10028 (comment)

Problem Definition

Before #9996, baseapp took care of runTx/runMsgs, and some adjacent stuff like branching the stores, panic recovery, indexing events in TM etc.

After #9996, all this logic are moved into middlewares (inside x/auth/middleware). Howerver, to not overload PRs (#10028), tests that test baseapp runTx/runMsgs stuff are still kept in the baseapp_test package.

We should remove all middleware and tx execution tests out from baseapp_test into middleware_test.

Additionally, in #10028, when moving the tests from the baseapp to baseapp_test package, we introduced some technical debt (to access private baseapp fields) to solve cycle deps etc (see #10028 (comment)). All this can be removed as part of this refactor.

Proposal

• All tests in baseapp_test that need middleware should be moved into middleware_test
• Remove baseapp "test methods" introduced in refactor: migrate ante hanlders to middlewares #10028 (comment)

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[amaury1093]

We reverted middlewares so we can close this.

Superseded by #12802