ttl: add methods to split ttl scan tasks (#39627)

close #39626

Author: lcwangchao

ttl/cache/BUILD.bazel

@@ -12,16 +12,22 @@ go_library(
     visibility = ["//visibility:public"],
     deps = [
         "//infoschema",
+        "//kv",
         "//parser/ast",
         "//parser/model",
         "//parser/mysql",
+        "//parser/terror",
         "//sessionctx",
         "//table/tables",
+        "//tablecodec",
         "//ttl/session",
         "//types",
         "//util/chunk",
+        "//util/codec",
         "//util/logutil",
+        "//util/mathutil",
         "@com_github_pingcap_errors//:errors",
+        "@com_github_tikv_client_go_v2//tikv",
         "@org_uber_go_zap//:zap",
     ],
 )
@@ -32,20 +38,30 @@ go_test(
         "base_test.go",
         "infoschema_test.go",
         "main_test.go",
+        "split_test.go",
         "table_test.go",
         "ttlstatus_test.go",
     ],
     embed = [":cache"],
     flaky = True,
     deps = [
+        "//infoschema",
+        "//kv",
         "//parser",
         "//parser/model",
         "//server",
+        "//store/helper",
+        "//tablecodec",
         "//testkit",
         "//testkit/testsetup",
         "//ttl/session",
+        "//types",
+        "//util/codec",
+        "@com_github_pingcap_kvproto//pkg/metapb",
         "@com_github_stretchr_testify//assert",
         "@com_github_stretchr_testify//require",
+        "@com_github_tikv_client_go_v2//tikv",
+        "@com_github_tikv_pd_client//:client",
         "@org_uber_go_goleak//:goleak",
     ],
 )