hyper: re-use internal client, impl Default

[Fishrock123]

• Makes HyperClient impl Clone and Default
• Re-uses the internal hyper client for pooling and alloc efficiency
• Adds HyperClient::from_client()
• Always uses the HttpsConnector (has internal http fallback)

Required for hyper-client in Surf:
http-rs/surf#234

[Fishrock123]

Edit: actually nightly broke: rust-lang/rust#77089

That docs failure is not our own but rather async-std's

error[E0046]: not all trait items implemented, missing: `as_flags`
   --> /home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/async-std-1.6.4/src/fs/open_options.rs:303:5
    |
303 |     impl OpenOptionsExt for OpenOptions {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `as_flags` in implementation
    |
    = help: implement the missing item: `fn as_flags(&self) -> std::result::Result<i32, futures_io::Error> { todo!() }`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0046`.
error: could not compile `async-std`

To learn more, run the command again with --verbose.
warning: build failed, waiting for other jobs to finish...
error[E0046]: not all trait items implemented, missing: `as_flags`
   --> /home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/async-std-1.6.4/src/fs/open_options.rs:303:5
    |
303 |     impl OpenOptionsExt for OpenOptions {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `as_flags` in implementation
    |
    = help: implement the missing item: `fn as_flags(&self) -> std::result::Result<i32, futures_io::Error> { todo!() }`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0046`.
error: build failed
Error: Process completed with exit code 101.

[Fishrock123]

ok well, since this is feature flagged anyways I'm just gona merge it, since I want it for lambda.