[DSLX:cleanup] Move builtins X-macro to dslx_builtins translation unit.

This requires us to move signatures out to a different translation unit to
avoid a circular dependency with interpreter values.

PiperOrigin-RevId: 615595496

xls/dslx/BUILD

@@ -213,6 +213,7 @@ cc_library(
     srcs = ["interp_value.cc"],
     hdrs = ["interp_value.h"],
     deps = [
+        ":dslx_builtins",
         ":value_format_descriptor",
         "//xls/common:math_util",
         "//xls/common/logging",
@@ -371,6 +372,19 @@ cc_library(
     name = "dslx_builtins",
     srcs = ["dslx_builtins.cc"],
     hdrs = ["dslx_builtins.h"],
+    deps = [
+        "@com_google_absl//absl/base:no_destructor",
+        "@com_google_absl//absl/container:flat_hash_set",
+        "@com_google_absl//absl/status",
+        "@com_google_absl//absl/status:statusor",
+        "@com_google_absl//absl/strings:str_format",
+    ],
+)
+
+cc_library(
+    name = "dslx_builtins_signatures",
+    srcs = ["dslx_builtins_signatures.cc"],
+    hdrs = ["dslx_builtins_signatures.h"],
     deps = [
         ":channel_direction",
         ":errors",
@@ -392,8 +406,6 @@ cc_library(
         "@com_google_absl//absl/base:no_destructor",
         "@com_google_absl//absl/container:flat_hash_map",
         "@com_google_absl//absl/container:flat_hash_set",
-        "@com_google_absl//absl/log:check",
-        "@com_google_absl//absl/status",
         "@com_google_absl//absl/status:statusor",
         "@com_google_absl//absl/strings",
         "@com_google_absl//absl/strings:str_format",