Partial fee estimates for SubmittableExtrinsic (#910)

* add partial_fee estimation to submittable extrinsic

* add integration test

* make functions immune to doctest

* add doc test

* inline encoded_with_len, fix tests

* fix test fmt

* remove unused imoort

* Bump h2 from 0.3.16 to 0.3.17 (#911)

Bumps [h2](https://github.com/hyperium/h2) from 0.3.16 to 0.3.17.
- [Release notes](https://github.com/hyperium/h2/releases)
- [Changelog](https://github.com/hyperium/h2/blob/master/CHANGELOG.md)
- [Commits](https://github.com/hyperium/h2/compare/v0.3.16...v0.3.17)

---
updated-dependencies:
- dependency-name: h2
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

* call_raw returns Res: Decode

* remove import

* remove struct

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

testing/integration-tests/src/blocks/mod.rs

@@ -3,7 +3,7 @@
 // see LICENSE for license details.
 
 use crate::test_context;
-use codec::{Compact, Decode};
+use codec::Compact;
 use frame_metadata::RuntimeMetadataPrefixed;
 use futures::StreamExt;
 
@@ -101,10 +101,9 @@ async fn runtime_api_call() -> Result<(), subxt::Error> {
     let block = sub.next().await.unwrap()?;
     let rt = block.runtime_api().await?;
 
-    let bytes = rt.call_raw("Metadata_metadata", None).await?;
-    let cursor = &mut &*bytes;
-    let _ = <Compact<u32>>::decode(cursor)?;
-    let meta: RuntimeMetadataPrefixed = Decode::decode(cursor)?;
+    let (_, meta) = rt
+        .call_raw::<(Compact<u32>, RuntimeMetadataPrefixed)>("Metadata_metadata", None)
+        .await?;
     let metadata_call = match meta.1 {
         frame_metadata::RuntimeMetadata::V14(metadata) => metadata,
         _ => panic!("Metadata V14 unavailable"),