Declare MSRV for error-stack

[indietyp]

Is your feature request related to a problem? Please describe.

I am currently implementing #794. With the recent release of 1.63, I would like a clarification on the officially supported MSRV for error-stack 0.2.

This is expressed in two ways, which I'd consider blocking until a concrete ruling has been given.

1.63 stabilized explicit_generic_args_with_impl_trait, which is part of the current rework of the hook architecture.

https://github.com/indietyp/hash/blob/40e389247364eeac6cf955c60b8bbe9938da541e/packages/libs/error-stack/src/hook.rs#L54-L56

Another way would be that we would likely be able to drop the hooks feature if we set the MSRV to 1.63 and work with only std for hooks, as it currently brings in a new dependency once_cell, which we could fully replace by RwLock.

https://github.com/indietyp/hash/blob/40e389247364eeac6cf955c60b8bbe9938da541e/packages/libs/error-stack/src/hook.rs#L13-L18

The current hack that has been used to fix #873, could be rewritten to be more precise.

https://github.com/indietyp/hash/blob/40e389247364eeac6cf955c60b8bbe9938da541e/packages/libs/error-stack/src/report.rs#L246-L248

        let span_trace = if core::any::request_ref::<SpanTrace>(&provider)
            .filter(|span_trace| span_trace.status() == SpanTraceStatus::CAPTURED)
            .is_some()

(same with the Backtrace code)

This is because with the nightly version, after the stabilization of explicit_generic_args_with_impl_trait, the number of generics in request_ref was changed. We no longer need to employ the hackif we only support versions that have explicit_generic_args_with_impl_trait stabilized.

These are not necessarily deal breakers but could make the API more concise. To be able to implement them, an official MSRV is needed.

Describe the solution you'd like

README.md entry about the current MSRV and CI/CD tests for the MSRV.

Additional context

This has been discussed off GH with @TimDiekmann.