[Kernel] Further refactor and cleanup SnapshotManager (#4090)

#### Which Delta project/connector is this regarding?

- [ ] Spark
- [ ] Standalone
- [ ] Flink
- [X] Kernel
- [ ] Other (fill in here)

## Description

This PR further refactors and cleans up SnapshotManager. We consolidate
all of our `getLogSegment` methods to just one. It has a deep
implementation. This PR adds nice, clean header blocks to describe the
steps during log segment construction.

## How was this patch tested?

Refactor. Update existing UTs.

## Does this PR introduce _any_ user-facing changes?

No.

kernel/kernel-api/src/main/java/io/delta/kernel/internal/DeltaErrors.java

@@ -49,7 +49,7 @@ public static KernelException versionBeforeFirstAvailableCommit(
     return new KernelException(message);
   }
 
-  public static KernelException versionAfterLatestCommit(
+  public static KernelException versionToLoadAfterLatestCommit(
       String tablePath, long versionToLoad, long latestVersion) {
     String message =
         String.format(