Revert "Add new ImmutableBitSet#isMinimal API and check unique keys minimality in tests"

The codebase has already "minimization" code in various other places (e.g., RelMdUniqueKeys#filterSupersets) and there is overlapping functionality with the new isMinimal API.
Based on these findings, I don't think a new API is necessary thus I reverted the respective code changes from here.

If we want to add a new public API its better to refactor/use the existing "minimization" logic.
However, the refactoring will require some discussion on where to move the code and how we want the API to look like so it is out of the scope of this PR.

Author: zabetak

core/src/main/java/org/apache/calcite/util/ImmutableBitSet.java

@@ -978,18 +978,6 @@ public static boolean allContain(Collection<ImmutableBitSet> bitSets, int bit) {
     return true;
   }
 
-  /**
-   * Returns whether this is a minimal set with respect to the specified collection of bitSets.
-   */
-  public boolean isMinimal(Collection<ImmutableBitSet> bitSets) {
-    for (ImmutableBitSet other : bitSets) {
-      if (!this.equals(other) && this.contains(other)) {
-        return false;
-      }
-    }
-    return true;
-  }
-
   /** Returns whether a given predicate evaluates to true for all bits in this
    * set. */
   public boolean allMatch(IntPredicate predicate) {

core/src/test/java/org/apache/calcite/util/ImmutableBitSetTest.java

@@ -668,38 +668,6 @@ private List<ImmutableBitSet> getSortedList() {
     assertFalse(ImmutableBitSet.allContain(collection2, 4));
   }
 
-  @Test void testIsMinimal() {
-    ImmutableBitSet se = ImmutableBitSet.of();
-    ImmutableBitSet s0 = ImmutableBitSet.of(0);
-    ImmutableBitSet s1 = ImmutableBitSet.of(1);
-    ImmutableBitSet s01 = ImmutableBitSet.of(0, 1);
-
-    assertTrue(se.isMinimal(Collections.singletonList(se)));
-    assertTrue(se.isMinimal(Collections.singletonList(s0)));
-    assertTrue(se.isMinimal(Collections.singletonList(s1)));
-    assertTrue(se.isMinimal(Collections.singletonList(s01)));
-
-    assertFalse(s0.isMinimal(Collections.singletonList(se)));
-    assertTrue(s0.isMinimal(Collections.singletonList(s0)));
-    assertTrue(s0.isMinimal(Collections.singletonList(s1)));
-    assertTrue(s0.isMinimal(Collections.singletonList(s01)));
-
-    assertFalse(s1.isMinimal(Collections.singletonList(se)));
-    assertTrue(s1.isMinimal(Collections.singletonList(s0)));
-    assertTrue(s1.isMinimal(Collections.singletonList(s1)));
-    assertTrue(s1.isMinimal(Collections.singletonList(s01)));
-
-    assertFalse(s01.isMinimal(Collections.singletonList(se)));
-    assertFalse(s01.isMinimal(Collections.singletonList(s0)));
-    assertFalse(s01.isMinimal(Collections.singletonList(s1)));
-    assertTrue(s01.isMinimal(Collections.singletonList(s01)));
-
-    assertTrue(se.isMinimal(Arrays.asList(s0, s1)));
-    assertTrue(s0.isMinimal(Arrays.asList(s0, s1)));
-    assertTrue(s1.isMinimal(Arrays.asList(s0, s1)));
-    assertFalse(s01.isMinimal(Arrays.asList(s0, s1)));
-  }
-
   /**
    * Test case for {@link ImmutableBitSet#anyMatch(IntPredicate)}
    * and {@link ImmutableBitSet#allMatch(IntPredicate)}.

testkit/src/main/java/org/apache/calcite/test/RelMetadataFixture.java

@@ -356,7 +356,6 @@ public RelMetadataFixture assertThatUniqueKeysAre(
         ImmutableSortedSet.copyOf(result),
         is(ImmutableSortedSet.copyOf(expectedUniqueKeys)));
     checkUniqueConsistent(rel);
-    assertThat(result.stream().allMatch(s -> s.isMinimal(result)), is(true));
     return this;
   }