update solochain to use #[runtime] (#5772)
# Description * This is part of [issue 5242](https://github.com/paritytech/polkadot-sdk/issues/5242), specifically getting solochain to use `#[frame::runtime]` * Furthermore, reinforced the convention of `Template` instead of `TemplateModule` ## Integration * Should be integrated into the `solochain` template and documentation ## Review Notes * Refactored `solochain` template from [construct_runtime!](https://paritytech.github.io/polkadot-sdk/master/frame_support/macro.construct_runtime.html) to [#[runtime]](https://paritytech.github.io/polkadot-sdk/master/frame_support/attr.runtime.html). * AFAIU `Template` is our new convention, and preferred over `TemplateModule`. # Out of scope * The [#[runtime]](https://paritytech.github.io/polkadot-sdk/master/frame_support/attr.runtime.html) documentation is still very rudimentary, and should ideally be expanded to explain the macro, both what it does and the input options. * Furthermore, suggest update [#[runtime]](https://paritytech.github.io/polkadot-sdk/master/frame_support/attr.runtime.html) documentation to replace `#[crate::runtime]` with `#[frame_support::runtime]` --------- Co-authored-by: Jan-Jan <[email protected]> Co-authored-by: Oliver Tale-Yazdi <[email protected]> Co-authored-by: Shawn Tabrizi <[email protected]> Co-authored-by: command-bot <>