Update fileData & inlineData to kebab case

Google Gemini HTTP API requires file_data and inline_data to be in kebab case. This is different to the SDKs which use Snake case. 

It is possible to use Snake case but with mixed results (e.g. inlineData works, but fileData does not), however officially both should be kebab (see Shell docs): https://ai.google.dev/api/files and have been tested working.

libs/langchain-google-genai/src/utils/common.ts

@@ -75,17 +75,17 @@ export function convertAuthorToRole(
 function messageContentMedia(content: MessageContentComplex): Part {
   if ("mimeType" in content && "data" in content) {
     return {
-      inlineData: {
-        mimeType: content.mimeType,
+      inline_data: {
+        mime_type: content.mimeType,
         data: content.data,
       },
     };
   }
   if ("mimeType" in content && "fileUri" in content) {
     return {
-      fileData: {
-        mimeType: content.mimeType,
-        fileUri: content.fileUri,
+      file_data: {
+        mime_type: content.mimeType,
+        file_uri: content.fileUri,
       },
     };
   }
@@ -164,9 +164,9 @@ export function convertMessageContentToParts(
         }
 
         return {
-          inlineData: {
+          inline_data: {
             data,
-            mimeType,
+            mime_type: mimeType,
           },
         };
       } else if (c.type === "media") {
@@ -186,8 +186,8 @@ export function convertMessageContentToParts(
         typeof c.data === "string"
       ) {
         return {
-          inlineData: {
-            mimeType: c.type,
+          inline_data: {
+            mime_type: c.type,
             data: c.data,
           },
         };