Update CI to also test with MSRV

[notmandatory]

Looks like there was some a change in the dependencies for esplora-client 0.3 and CI is failing on bdk with it's MSRV 1.56.1. The CI for this project should be updated to test with rust stable and MSRV. Then we'll have to decide also what MSRV to use, ideally should be same as bdk but if not possible then bdk can keep using 0.2 for this project until able to update it's MSRV.

see: https://github.com/bitcoindevkit/bdk/actions/runs/3999121592/jobs/6862629601

cargo tree -i -p rustls@0.20.8 --features minimal,use-esplora-blocking --no-default-features
rustls v0.20.8
└── ureq v2.6.2
    └── esplora-client v0.3.0
        └── bdk v0.26.0 (/Users/steve/git/notmandatory/bdk)
    [build-dependencies]
    └── electrsd v0.21.1
        [dev-dependencies]
        └── bdk v0.26.0 (/Users/steve/git/notmandatory/bdk)

[notmandatory]

Ugh, looks like rustls changed their MSRV to 1.57 on 2023-01-12 with a point release from 0.20.7 to 0.20.8, rustls/rustls#1152. 😞

https://github.com/rustls/rustls/blob/main/README.md

[notmandatory]

I created a PR to change BDK MSRV to 1.57.0, we can discuss more here: bitcoindevkit/bdk#842