feat(xcm): support json schema (for CosmWasm VM support) (#1454)

# Description

- What does this PR do? Allows to generate JSON schema for subset of XCM
in std builds
- Why are these changes needed? To support XCM messages in CosmWasm
contracts which require Schemars to generate contract clients
- How were these changes implemented and what do they affect? We will
use schema feature flag to build XCM pallet with JSON schema enabled

# Checklist

- [x] My PR includes a detailed description as outlined in the
"Description" section above
- [x] My PR follows the [labeling requirements](CONTRIBUTING.md#Process)
of this project (at minimum one label for `T`
  required)
- [x] I have made corresponding changes to the documentation (if
applicable)
- [x] I have added tests that prove my fix is effective or that my
feature works (if applicable)
- [x] If this PR alters any external APIs or interfaces used by
Polkadot, the corresponding Polkadot PR is ready as well
  as the corresponding Cumulus PR (optional)

Cargo.lock

@@ -1521,13 +1521,14 @@ dependencies = [
 
 [[package]]
 name = "bounded-collections"
-version = "0.1.8"
+version = "0.1.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "eb5b05133427c07c4776906f673ccf36c21b102c9829c641a5b56bd151d44fd6"
+checksum = "ca548b6163b872067dc5eb82fd130c56881435e30367d2073594a3d9744120dd"
 dependencies = [
  "log",
  "parity-scale-codec",
  "scale-info",
+ "schemars",
  "serde",
 ]
 
@@ -16344,6 +16345,30 @@ dependencies = [
  "windows-sys 0.48.0",
 ]
 
+[[package]]
+name = "schemars"
+version = "0.8.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "763f8cd0d4c71ed8389c90cb8100cba87e763bd01a8e614d4f0af97bcd50a161"
+dependencies = [
+ "dyn-clone",
+ "schemars_derive",
+ "serde",
+ "serde_json",
+]
+
+[[package]]
+name = "schemars_derive"
+version = "0.8.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ec0f696e21e10fa546b7ffb1c9672c6de8fbc7a81acf59524386d8639bf12737"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "serde_derive_internals",
+ "syn 1.0.109",
+]
+
 [[package]]
 name = "schnellru"
 version = "0.2.1"
@@ -16614,6 +16639,17 @@ dependencies = [
  "syn 2.0.39",
 ]
 
+[[package]]
+name = "serde_derive_internals"
+version = "0.26.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "85bf8229e7920a9f636479437026331ce11aa132b4dde37d121944a44d6e5f3c"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 1.0.109",
+]
+
 [[package]]
 name = "serde_fmt"
 version = "1.0.3"
@@ -18117,6 +18153,7 @@ dependencies = [
  "bounded-collections",
  "parity-scale-codec",
  "scale-info",
+ "schemars",
  "serde",
  "smallvec",
  "sp-arithmetic",
@@ -18353,6 +18390,7 @@ dependencies = [
  "log",
  "parity-scale-codec",
  "scale-info",
+ "schemars",
  "serde",
  "sp-io",
  "sp-weights",