fix: merge get_np_precision to get_xp_precision (#4867)

`get_xp_precision` is more general and has more precisions (including
bfloat16).

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Refactor**
* Improved internal handling of precision settings for numerical
operations, streamlining how precision is determined. No changes to
user-facing functionality.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Signed-off-by: Jinzhe Zeng <jinzhe.zeng@ustc.edu.cn>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: njzjz

deepmd/common.py

@@ -35,6 +35,7 @@
 )
 
 __all__ = [
+    "GLOBAL_NP_FLOAT_PRECISION",
     "VALID_ACTIVATION",
     "VALID_PRECISION",
     "expand_sys_str",
@@ -249,16 +250,11 @@ def get_np_precision(precision: "_PRECISION") -> np.dtype:
     RuntimeError
         if string is invalid
     """
-    if precision == "default":
-        return GLOBAL_NP_FLOAT_PRECISION
-    elif precision == "float16":
-        return np.float16
-    elif precision == "float32":
-        return np.float32
-    elif precision == "float64":
-        return np.float64
-    else:
-        raise RuntimeError(f"{precision} is not a valid precision")
+    from deepmd.dpmodel.common import (
+        get_xp_precision,
+    )
+
+    return get_xp_precision(np, precision)
 
 
 def symlink_prefix_files(old_prefix: str, new_prefix: str) -> None: