refactor(compress): expose sequence statistics leaves from Rust

The C definitions of ZSTD_get1BlockSummary() and ZSTD_resetSeqStore()
only forwarded their arguments to Rust, so they duplicated the ABI boundary
without contributing assertions, private-state adaptation, or C-only policy.
Make Rust provide the existing internal symbols directly and remove only the
corresponding C declarations and forwarding bodies. Keep crate-local aliases
for the current compressor-module imports; they are Rust name aliases and do
not add the former ABI symbols back. No other statistics leaf is included.

Test Plan:
- `ulimit -v 41943040; cc -Ilib -Ilib/common -Ilib/compress -Ilib/decompress -Ilib/dictBuilder -Ilib/legacy -Ilib/deprecated -Ilib/zstd -fsyntax-only lib/compress/zstd_compress.c` -- passed
- `ulimit -v 41943040; cargo +nightly fmt --manifest-path rust/Cargo.toml --all -- --check` -- passed
- `git diff --check` and `git diff --cached --check` -- passed
- No cargo builds, make commands, or tests run, per request

rust/src/zstd_compress_stats.rs

@@ -227,7 +227,7 @@ pub unsafe extern "C" fn ZSTD_rust_convertSequencesNoRepcodes(
 /// `ZSTD_get1BlockSummary()`; the delimiter is identified by zero match
 /// length and contributes its literal length to the totals.
 #[no_mangle]
-pub unsafe extern "C" fn ZSTD_rust_get1BlockSummary(
+pub unsafe extern "C" fn ZSTD_get1BlockSummary(
     seqs: *const ZSTD_Sequence,
     nb_seqs: usize,
 ) -> BlockSummary {
@@ -261,6 +261,10 @@ pub unsafe extern "C" fn ZSTD_rust_get1BlockSummary(
     invalid()
 }
 
+// Keep the old crate-local names for callers in the compressor module. These
+// aliases do not create additional ABI symbols.
+pub(crate) use ZSTD_get1BlockSummary as ZSTD_rust_get1BlockSummary;
+
 /// Estimates the literal-section size used by the block splitter.
 unsafe fn estimate_block_size_literal(
     literals: *const u8,
@@ -1128,13 +1132,15 @@ pub unsafe extern "C" fn ZSTD_rust_storeLastLiterals(
 
 /// Resets the sequence and literal cursors for a new block.
 #[no_mangle]
-pub unsafe extern "C" fn ZSTD_rust_resetSeqStore(seq_store: *mut SeqStore_t) {
+pub unsafe extern "C" fn ZSTD_resetSeqStore(seq_store: *mut SeqStore_t) {
     let seq_store = unsafe { &mut *seq_store };
     seq_store.lit = seq_store.litStart;
     seq_store.sequences = seq_store.sequencesStart;
     seq_store.longLengthType = 0;
 }
 
+pub(crate) use ZSTD_resetSeqStore as ZSTD_rust_resetSeqStore;
+
 /// Returns the sum of all literal and match lengths in an external sequence
 /// buffer, without looking for a block delimiter.
 #[no_mangle]
@@ -2682,7 +2688,7 @@ mod tests {
             },
         ];
 
-        let summary = unsafe { ZSTD_rust_get1BlockSummary(sequences.as_ptr(), sequences.len()) };
+        let summary = unsafe { ZSTD_get1BlockSummary(sequences.as_ptr(), sequences.len()) };
 
         assert_eq!(summary.nbSequences, 2);
         assert_eq!(summary.blockSize, 12);
@@ -2697,13 +2703,13 @@ mod tests {
             matchLength: 4,
             rep: 0,
         }];
-        let missing = unsafe { ZSTD_rust_get1BlockSummary(sequences.as_ptr(), sequences.len()) };
+        let missing = unsafe { ZSTD_get1BlockSummary(sequences.as_ptr(), sequences.len()) };
         assert_eq!(
             missing.nbSequences,
             ERROR(ZstdErrorCode::ExternalSequencesInvalid)
         );
 
-        let empty = unsafe { ZSTD_rust_get1BlockSummary(std::ptr::null(), 0) };
+        let empty = unsafe { ZSTD_get1BlockSummary(std::ptr::null(), 0) };
         assert_eq!(
             empty.nbSequences,
             ERROR(ZstdErrorCode::ExternalSequencesInvalid)
@@ -3369,7 +3375,7 @@ mod tests {
             longLengthPos: 11,
         };
 
-        unsafe { ZSTD_rust_resetSeqStore(&mut seq_store) };
+        unsafe { ZSTD_resetSeqStore(&mut seq_store) };
 
         assert_eq!(seq_store.sequences, sequences_start);
         assert_eq!(seq_store.lit, literals_start);