Dataframe v2: support for clear semantics (#7652)

Support clear semantics in the dataframe API.
Tombstones are never visible to end-users, only their effect.

Like every other Dataframe v2 feature PR, and following recommendations
from @jleibs, this prioritizes convenience of implementation over
everything else, for now.
All clear chunks are fetched, post-processed, and re-injected into the
view contents during init(), and then the streaming join runs as usual
after that.

Static clear semantics can get pretty unhinged, but that's A) not
specific to the dataframe API and B) so extremely niche that our time is
better spent on real-world problems right now:
- #7650 
- #7631 

---

- Fixes #7495
- Fixes #7414
- Fixes #7468
- Fixes #7493
- DNM: requires #7649

crates/store/re_chunk_store/src/dataframe.rs

@@ -6,10 +6,10 @@ use arrow2::{
     array::ListArray as ArrowListArray,
     datatypes::{DataType as ArrowDatatype, Field as ArrowField},
 };
+use nohash_hasher::IntSet;
 
 use re_chunk::TimelineName;
-use re_log_types::ResolvedTimeRange;
-use re_log_types::{EntityPath, TimeInt, Timeline};
+use re_log_types::{EntityPath, ResolvedTimeRange, TimeInt, Timeline};
 use re_types_core::{ArchetypeName, ComponentName};
 
 use crate::ChunkStore;
@@ -765,12 +765,22 @@ impl ChunkStore {
                 })
             });
 
+        use re_types_core::Archetype as _;
+        let clear_related_components: IntSet<ComponentName> =
+            re_types_core::archetypes::Clear::all_components()
+                .iter()
+                .copied()
+                .collect();
+
         let components = static_components
             .chain(temporal_components)
             .filter(|col| match col {
                 ColumnDescriptor::Time(_) => true,
                 ColumnDescriptor::Component(descr) => {
-                    !descr.component_name.is_indicator_component()
+                    let is_indicator = descr.component_name.is_indicator_component();
+                    // Tombstones are not exposed to end users -- only their _effect_.
+                    let is_tombstone = clear_related_components.contains(&descr.component_name);
+                    !is_indicator && !is_tombstone
                 }
             })
             .collect::<BTreeSet<_>>();