Use filer-side copy for mounted whole-file copy_file_range (#8747)

* Optimize mounted whole-file copy_file_range

* Address mounted copy review feedback

* Harden mounted copy fast path

---------

Co-authored-by: Copilot <copilot@github.com>

weed/filer/copy_params.go

@@ -0,0 +1,17 @@
+package filer
+
+const (
+	CopyQueryParamFrom             = "cp.from"
+	CopyQueryParamOverwrite        = "overwrite"
+	CopyQueryParamDataOnly         = "dataOnly"
+	CopyQueryParamRequestID        = "copy.requestId"
+	CopyQueryParamSourceInode      = "copy.srcInode"
+	CopyQueryParamSourceMtime      = "copy.srcMtime"
+	CopyQueryParamSourceSize       = "copy.srcSize"
+	CopyQueryParamDestinationInode = "copy.dstInode"
+	CopyQueryParamDestinationMtime = "copy.dstMtime"
+	CopyQueryParamDestinationSize  = "copy.dstSize"
+
+	CopyResponseHeaderCommitted = "X-SeaweedFS-Copy-Committed"
+	CopyResponseHeaderRequestID = "X-SeaweedFS-Copy-Request-ID"
+)