Restructure merkle ledger tests

[glyh]

Simple noop moving tests around.

[glyh]

!ci-build-me

[georgeee]

!ci-bypass-changelog

[georgeee]

!ci-build-me

[dannywillems]

!ci-build-me

[glyh]

@dannywillems I would rewrite this to fit your requirements later :)

[dannywillems]

@dannywillems I would rewrite this to fit your requirements later :)

Ah, thanks! CI fails with

File "src/lib/syncable_ledger/test/dune", line 24, characters 2-21:
24 |   merkle_ledger_tests
       ^^^^^^^^^^^^^^^^^^^
Error: Library "merkle_ledger_tests" not found.
-> required by library "test" in _build/default/src/lib/syncable_ledger/test
-> required by
   _build/default/src/lib/syncable_ledger/test/.test.objs/native/test.cmx
-> required by _build/default/src/lib/syncable_ledger/test/test.a
-> required by alias src/lib/syncable_ledger/test/all
-> required by alias src/lib/default

[cjjdespres]

The build fails because merkle_ledger_tests was removed as a package, but it's still listed as a dependency of the syncable ledger tests:

https://github.com/MinaProtocol/mina/blob/16d0321b99480b5a8e6b664c2adc97bbe56994c1/src/lib/syncable_ledger/test/dune#L24

The syncable ledger tests need access to the Merkle_ledger_tests.Test_stubs, but those are now in merkle_ledger/test/test_stubs.ml. Also, they're not exposed as a library in that new location.

[glyh]

Close in favor of https://github.com/MinaProtocol/mina/pull/17486