update reqwest dependency and add re-export reqwest::Client

[jmwample]

Update the dependency on reqwest to the latest minor version.

Add a type alias that allows downstream libraries to construct and provide an underlying reqwest::Client without being forced to match the library version in their code. i.e. this allows things like:

use tendermint_rpc::{HttpClient, Client, client::{CompatMode, http::ReqwestClient}};

#[tokio::main]
async fn main() {

    // Name your user agent after your app?
    static APP_USER_AGENT: &str = concat!(
        env!("CARGO_PKG_NAME"),
        "/",
        env!("CARGO_PKG_VERSION"),
   );

    let inner = ReqwestClient::builder()
        .user_agent(APP_USER_AGENT)
        .hickory_dns(true)
        .build()
        .unwrap();

    let client = HttpClient::builder("http://127.0.0.1:26657")
        .client(inner)
        .compat_mode(CompatMode::V0_37)
        .build()
        .unwrap();

    let abci_info = client.abci_info()
        .await
        .unwrap();

    println!("Got ABCI info: {:?}", abci_info);
}

---

• Referenced an issue explaining the need for the change
• Updated all relevant documentation in docs
• Updated all code comments where relevant
• Wrote tests
• Added entry in .changelog/

---

Note

Updates reqwest to 0.12 and adds a re-exported InnerClient alias used across HttpClient APIs for easier client injection.

• RPC HTTP client:
  • Dependency: Bump reqwest from 0.11.20 to 0.12 in rpc/Cargo.toml.
  • Client re-export: Add pub type InnerClient = reqwest::Client; and switch HttpClient internals/Builder/new_from_parts to use InnerClient.
• Changelog: Add entry noting the reqwest update and reqwest::Client re-export.

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[pronebird]

Can this be reviewed please. reqwest 0.11 pulls hyper v0.14.32 which is really old. reqwest 0.13 is already out too. Thank you. @melekes