chore(msrv): set to 1.70

[0x61nas]

It will be helpful for the down stream crates to know what the minimum supported Rust version (MSRV) for their dependencies so they can decide how to bump their version and when, because it's considered as a breaking change

[kwinz]

I am not sure why the CI test results are not showing for the branch here? I believe a maintainer merged a pull request changing the workflow file about a month ago, but the changes to the config weren't approved after merging them. Apparently the integration tests are still being run with the old config, but the results aren't showing up in the pull requests because of the missing approval. Can the maintainers please approve the continuous integration workflow config changes (or revert them)?
I can see that the tests are already failing so bugs or coding issues have probably already made it into the release unnoticed!