Introduce tail estimation to prevent oversized compaction files (#14051)

Summary:
**Summary:**
This change introduces tail size estimation during SST construction to improve compaction file cutting accuracy to prevent oversized files. The BlockBasedTableBuilder now estimates the SST tail size (index and filter blocks) and uses this estimate, in addition to the data size, to determine when to cut files during compaction.

**Problem:**
Currently, file cutting logic only considers data size when determining where to cut a file, failing to reserve space for index and filter blocks that are added when the file is finalized. This often leads to SST files that exceed target file size limits.

**Behavior Change:**
Implement size estimation methods for index and filter builders, and integrate these estimates into BlockBasedTableBuilder via a new EstimatedTailSize() method. This method aggregates estimates from all tail components and is used for file cutting decisions during compaction.

**Performance Considerations:**
To minimize CPU overhead, size estimates are updated when data blocks are finalized rather than on every key add. For index builders, estimates are updated when index entries are added (one per data block). For filter builders, the OnDataBlockFinalized() hook triggers estimate updates when data blocks are cut/finalized.

This approach provides:
* Minimal impact to compaction hot path (key additions)
* Near real-time estimates for file cutting decisions
* Meaningful estimate changes only when data blocks are finalized

**Usage:**
* Set true mutable cf option `compaction_use_tail_size_estimation`
to use tail size estimation for compaction file cutting decisions.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/14051

Test Plan:
* Assert tail size estimate is an overestimate in BlockBasedTableBuilder::Finish
* Add new test to verify compaction output file is below target file size

**Next steps:**
* Enable tail size estimation for compaction file cutting by default (and other improvements)

Reviewed By: pdillinger, cbi42

Differential Revision: D84852285

Pulled By: nmk70

fbshipit-source-id: c43cf5dbd2cb2f623a0622591ef24eee30ce0c87

BUCK

@@ -5194,12 +5194,6 @@ cpp_unittest_wrapper(name="import_column_family_test",
             extra_compiler_flags=[])
 
 
-cpp_unittest_wrapper(name="index_builder_test",
-            srcs=["table/block_based/index_builder_test.cc"],
-            deps=[":rocksdb_test_lib"],
-            extra_compiler_flags=[])
-
-
 cpp_unittest_wrapper(name="inlineskiplist_test",
             srcs=["memtable/inlineskiplist_test.cc"],
             deps=[":rocksdb_test_lib"],