refactor: 13270 Moved State API classes from `platform-core` to `state-api` module

[imalygin]

Description:

PR highlights:

• Moved classes related to the State API to state-api module
• Updated module-info.java definitions accordingly
• Removed SingletonStateTestBase and WritableSingletonStateBaseTest from hedera-app because they are copies of these classes in state-api that were created in https://github.com/hashgraph/hedera-services/pull/12570, and now they are no longer needed.
• Removed ReadableKVStateBaseTest, ReadableSingletonStateBaseTest and WritableKVStateBaseTest from swirlds-platform-core because they are copies of these classes in state-api that were created in https://github.com/hashgraph/hedera-services/pull/12570, and now they are no longer needed.
• Deleted ClassLoaderHelper as it's no longer in use

Related issue(s):

Fixes #13270

Notes for reviewer:

Checklist

• [ ] Documented (Code comments, README, etc.)
• [ ] Tested (unit, integration, etc.)

[github-actions[bot]]

Node: HAPI Test (Restart) Results

7 files  7 suites   8m 24s :stopwatch: 6 tests 6 :white_check_mark: 0 :zzz: 0 :x: 7 runs  7 :white_check_mark: 0 :zzz: 0 :x:

Results for commit d70acec6.

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Node: HAPI Test (Node Death Reconnect) Results

3 tests   3 :white_check_mark:  6m 42s :stopwatch: 3 suites  0 :zzz: 3 files    0 :x:

Results for commit d70acec6.

:recycle: This comment has been updated with latest results.

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Node: HAPI Test (Token) Results

 22 files   22 suites   6m 19s :stopwatch: 272 tests 272 :white_check_mark: 0 :zzz: 0 :x: 351 runs  351 :white_check_mark: 0 :zzz: 0 :x:

Results for commit d70acec6.

:recycle: This comment has been updated with latest results.

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Node: HAPI Test (Crypto) Results

 24 files   24 suites   16m 18s :stopwatch: 366 tests 366 :white_check_mark: 0 :zzz: 0 :x: 374 runs  374 :white_check_mark: 0 :zzz: 0 :x:

Results for commit d70acec6.

:recycle: This comment has been updated with latest results.

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Node: HAPI Test (Time Consuming) Results

19 tests   19 :white_check_mark:  23m 54s :stopwatch:  4 suites   0 :zzz:  4 files     0 :x:

Results for commit d70acec6.

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Node: HAPI Test (Smart Contract) Results

 79 files   79 suites   21m 2s :stopwatch: 689 tests 689 :white_check_mark: 0 :zzz: 0 :x: 750 runs  750 :white_check_mark: 0 :zzz: 0 :x:

Results for commit d70acec6.

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Node: HAPI Test (Misc) Results

 52 files   52 suites   17m 30s :stopwatch: 347 tests 347 :white_check_mark: 0 :zzz: 0 :x: 369 runs  369 :white_check_mark: 0 :zzz: 0 :x:

Results for commit d70acec6.

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Node: Unit Test Results

  1 532 files    1 532 suites   3h 38m 48s :stopwatch: 115 771 tests 115 712 :white_check_mark: 59 :zzz: 0 :x: 123 976 runs  123 917 :white_check_mark: 59 :zzz: 0 :x:

Results for commit d70acec6.

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[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 57.98%. Comparing base (9973fae) to head (c9b922b). Report is 122 commits behind head on develop.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #13971 +/- ## ============================================= - Coverage 67.58% 57.98% -9.61% + Complexity 36486 21956 -14530 ============================================= Files 3732 2857 -875 Lines 149767 110039 -39728 Branches 15571 11262 -4309 ============================================= - Hits 101223 63804 -37419 + Misses 44179 42660 -1519 + Partials 4365 3575 -790 ```

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