traces/tracing feature are inconsistently defined and used

[z0w13]

There's both cfg(feature = "traces") and cfg(feature = "tracing") which are both the same feature as far as I can tell.

This works fine when enabling the traces feature as it creates the implicit tracing feature as its dependency

Ideally the feature would be defined as traces = ["dep:tracing"] and not an an implicit feature, unless I'm missing why you'd want both traces/tracing as features? Also, the feature check in the source files would consistently use traces.

I ran into this because I accidentally enabled tracing instead of traces and got some confusing compilation errors.

[gftea]

we should replace all [cfg(feature = "tracing")] to [cfg(feature = "traces")] in codes.
We can not use dep:tracing because not supported if MSRV is 1.56 which was the goal of 1st release

[michaelklishin]

Alternatively the library can do that, then bump the major and the MSRV version to switch to tracing.

[gftea]

MSRV helps the lib to be widely compatible, we only need to bump MSRV when necessary.
I abondoned some nice syntax in new rust version in order to maintain as lowest MSRV as possible.
The v1.x, we will keep this, but if in the v2, we already bump msrv to higher due to rustls upgrade, then we can make it