vinyl: fix memory leak on dump/compaction failure

The issue is we increment `page_count` only on page write. If we fail
for some reason before then page info `min_key` in leaked.

LSAN report for 'vinyl/recovery_quota.test.lua':

```
2024-07-05 13:30:34.605 [478603] main/103/on_shutdown vy_scheduler.c:1668 E> 512/0: failed to compact range (-inf..inf)

=================================================================
==478603==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 4 byte(s) in 1 object(s) allocated from:
    #0 0x5e4ebafcae09 in malloc (/home/shiny/dev/tarantool/build-asan-debug/src/tarantool+0x1244e09) (BuildId: 20c5933d67a3831c4f43f6860379d58d35b81974)
    tarantool#1 0x5e4ebb3f9b69 in vy_key_dup /home/shiny/dev/tarantool/src/box/vy_stmt.c:308:14
    tarantool#2 0x5e4ebb49b615 in vy_page_info_create /home/shiny/dev/tarantool/src/box/vy_run.c:257:23
    tarantool#3 0x5e4ebb48f59f in vy_run_writer_start_page /home/shiny/dev/tarantool/src/box/vy_run.c:2196:6
    tarantool#4 0x5e4ebb48c6b6 in vy_run_writer_append_stmt /home/shiny/dev/tarantool/src/box/vy_run.c:2287:6
    tarantool#5 0x5e4ebb72877f in vy_task_write_run /home/shiny/dev/tarantool/src/box/vy_scheduler.c:1132:8
    tarantool#6 0x5e4ebb73305e in vy_task_compaction_execute /home/shiny/dev/tarantool/src/box/vy_scheduler.c:1485:9
    tarantool#7 0x5e4ebb73e152 in vy_task_f /home/shiny/dev/tarantool/src/box/vy_scheduler.c:1795:6
    tarantool#8 0x5e4ebb01e0b1 in fiber_cxx_invoke(int (*)(__va_list_tag*), __va_list_tag*) /home/shiny/dev/tarantool/src/lib/core/fiber.h:1331:10
    tarantool#9 0x5e4ebc389ee0 in fiber_loop /home/shiny/dev/tarantool/src/lib/core/fiber.c:1182:18
    tarantool#10 0x5e4ebd3e9595 in coro_init /home/shiny/dev/tarantool/third_party/coro/coro.c:108:3

SUMMARY: AddressSanitizer: 4 byte(s) leaked in 1 allocation(s).
```

NO_TEST=covered by existing tests (ASAN build)
NO_DOC=bugfix

Author: nshy

changelogs/unreleased/fix-memory-leak-in-vinyl-on-dump-failure.md

@@ -0,0 +1,3 @@
+## bugfix/vinyl
+
+- Fixed memory leak in vinyl on dump/compaction failure.

src/box/vy_run.c

@@ -2196,6 +2196,7 @@ vy_run_writer_start_page(struct vy_run_writer *writer,
 	if (vy_page_info_create(page, writer->data_xlog.offset,
 				key, writer->cmp_def) != 0)
 		return -1;
+	run->info.page_count++;
 	xlog_tx_begin(&writer->data_xlog);
 	return 0;
 }
@@ -2219,7 +2220,7 @@ vy_run_writer_write_to_page(struct vy_run_writer *writer, struct vy_entry entry)
 	writer->last = entry;
 	vy_stmt_ref_if_possible(entry.stmt);
 	struct vy_run *run = writer->run;
-	struct vy_page_info *page = run->page_info + run->info.page_count;
+	struct vy_page_info *page = run->page_info + run->info.page_count - 1;
 	uint32_t *offset = (uint32_t *)ibuf_alloc(&writer->row_index_buf,
 						  sizeof(uint32_t));
 	if (offset == NULL) {
@@ -2247,7 +2248,8 @@ static int
 vy_run_writer_end_page(struct vy_run_writer *writer)
 {
 	struct vy_run *run = writer->run;
-	struct vy_page_info *page = run->page_info + run->info.page_count;
+	assert(run->info.page_count > 0);
+	struct vy_page_info *page = run->page_info + run->info.page_count - 1;
 
 	assert(page->row_count > 0);
 	assert(ibuf_used(&writer->row_index_buf) ==
@@ -2269,7 +2271,6 @@ vy_run_writer_end_page(struct vy_run_writer *writer)
 	if (written < 0)
 		return -1;
 	page->size = written;
-	run->info.page_count++;
 	vy_run_acct_page(run, page);
 	ibuf_reset(&writer->row_index_buf);
 	return 0;