Refactor tsi_ssl_credentials target. (grpc#29443)

* Refactor tsi_ssl_credentials target.

BUILD

@@ -4646,23 +4646,43 @@ grpc_cc_library(
     ],
 )
 
+grpc_cc_library(
+    name = "tsi_ssl_session_cache",
+    srcs = [
+        "src/core/tsi/ssl/session_cache/ssl_session_boringssl.cc",
+        "src/core/tsi/ssl/session_cache/ssl_session_cache.cc",
+        "src/core/tsi/ssl/session_cache/ssl_session_openssl.cc",
+    ],
+    hdrs = [
+        "src/core/tsi/ssl/session_cache/ssl_session.h",
+        "src/core/tsi/ssl/session_cache/ssl_session_cache.h",
+    ],
+    external_deps = [
+        "absl/strings",
+        "absl/memory",
+        "libssl",
+        "libcrypto",
+    ],
+    language = "c++",
+    visibility = ["@grpc:public"],
+    deps = [
+        "gpr_base",
+        "grpc_base",
+    ],
+)
+
 grpc_cc_library(
     name = "tsi_ssl_credentials",
     srcs = [
         "src/core/lib/security/security_connector/ssl_utils.cc",
         "src/core/lib/security/security_connector/ssl_utils_config.cc",
         "src/core/tsi/ssl/key_logging/ssl_key_logging.cc",
-        "src/core/tsi/ssl/session_cache/ssl_session_boringssl.cc",
-        "src/core/tsi/ssl/session_cache/ssl_session_cache.cc",
-        "src/core/tsi/ssl/session_cache/ssl_session_openssl.cc",
         "src/core/tsi/ssl_transport_security.cc",
     ],
     hdrs = [
         "src/core/lib/security/security_connector/ssl_utils.h",
         "src/core/lib/security/security_connector/ssl_utils_config.h",
         "src/core/tsi/ssl/key_logging/ssl_key_logging.h",
-        "src/core/tsi/ssl/session_cache/ssl_session.h",
-        "src/core/tsi/ssl/session_cache/ssl_session_cache.h",
         "src/core/tsi/ssl_transport_security.h",
     ],
     external_deps = [
@@ -4681,6 +4701,7 @@ grpc_cc_library(
         "grpc_transport_chttp2_alpn",
         "ref_counted_ptr",
         "tsi_base",
+        "tsi_ssl_session_cache",
         "tsi_ssl_types",
         "useful",
     ],