Revert "feat(pageserver): repartition on L0-L1 boundary (#10548)" (#10870)

This reverts commit 443c8d0b4b.

## Problem

We observe a massive amount of compaction errors.

## Summary of changes

If the tenant did not write any L1 layers (i.e., they accumulate L0
layers where number of them is below L0 threshold), image creation will
always fail. Therefore, it's not correct to simply use the
disk_consistent_lsn or L0/L1 boundary for the image creation.

test_runner/regress/test_layers_from_future.py

@@ -20,9 +20,6 @@ from fixtures.remote_storage import LocalFsStorage, RemoteStorageKind
 from fixtures.utils import query_scalar, wait_until
 
 
-@pytest.mark.skip(
-    reason="We won't create future layers any more after https://github.com/neondatabase/neon/pull/10548"
-)
 @pytest.mark.parametrize(
     "attach_mode",
     ["default_generation", "same_generation"],