Update lowest supported Rust toolchain to 1.58

[mulkieran]

We'll plan to do this sometime in February and expect that it will 1.54 + 4 (+1) = 1.58 (1.59).

There are three places where value should be bumped to 1.58.1:

• LOWEST SUPPORTED RUST TOOLCHAIN value in all GitHub workflows for Stratis repos
• msrv value in .clippy.toml for all Stratis Rust repos
• Values in non GitHub-workflows tests

[mulkieran]

We can make use of the rust-version field and possibly drop the .clippy.toml file entirely (if clippy respects this field).

[mulkieran]

Upstream rust issue for existing bug: rust-lang/rust#94505..

[mulkieran]

Wait until April for this. Upstream bug fix has been merged...

[mulkieran]

Since it's actually 1.58 we can do it at any time.

[mulkieran]

I want to postpone a little longer, so that we can do the packaged build testing that we do in ci easily.

[mulkieran]

Does our packaged build testing require this any more. I think not.