[Bug Fix] Missing CustomOp SchemaRegister when generator EPContext ONNX model (#23091)

### Description
Enhancements to EPContext Operations:
1. Introduced support for the bfloat16 data type in EPContext operations.
2. Bug Fix: Missing Custom OP Schema Registration when generator EPContext ONNX model

---------

Co-authored-by: mingyue <mingyue@xilinx.com>
Co-authored-by: Hector Li <hecli@microsoft.com>

Author: 3 people

docs/ContribOperators.md

@@ -1625,7 +1625,7 @@ This version of the operator has been available since version 1 of the 'com.micr
 #### Type Constraints
 
 <dl>
-<dt><tt>T</tt> : tensor(int8), tensor(int16), tensor(int32), tensor(int64), tensor(uint8), tensor(uint16), tensor(uint32), tensor(uint64), tensor(float16), tensor(float), tensor(double)</dt>
+<dt><tt>T</tt> : tensor(int8), tensor(int16), tensor(int32), tensor(int64), tensor(uint8), tensor(uint16), tensor(uint32), tensor(uint64), tensor(float16), tensor(float), tensor(double), tensor(bfloat16)</dt>
 <dd>Constrain input and output types.</dd>
 </dl>
 

onnxruntime/core/framework/graph_partitioner.cc

@@ -681,7 +681,7 @@ static Status CreateEpContextModel(const ExecutionProviders& execution_providers
                            context_cache_path, "' exist already.");
   }
 
-  Model ep_context_model(graph.Name(), false, graph.GetModel().MetaData(), PathString(), IOnnxRuntimeOpSchemaRegistryList(),
+  Model ep_context_model(graph.Name(), false, graph.GetModel().MetaData(), PathString(), IOnnxRuntimeOpSchemaRegistryList{graph.GetSchemaRegistry()},
                          graph.DomainToVersionMap(), {}, logger);
   auto& ep_graph = ep_context_model.MainGraph();
   ep_graph.SetDescription(graph.Description());

onnxruntime/core/graph/contrib_ops/contrib_defs.cc

@@ -3371,7 +3371,8 @@ void RegisterContribSchemas() {
            "tensor(uint64)",
            "tensor(float16)",
            "tensor(float)",
-           "tensor(double)"},
+           "tensor(double)",
+           "tensor(bfloat16)"},
           "Constrain input and output types.");
 
   static const char* BitmaskDropout_ver1_doc = R"DOC(