Upgrade bitcoin dependency

[tcharding]

This update breaks MSRV 1.29 so cannot be merged until we merge: #222

Upgrade rust-bitcoin dependency to the newly released version (0.29.0). Includes fixing newly deprecated APIs.

• Patch one does the upgrade
• Patch two bumps the crate version and adds release notes

[dpc]

++ cargo generate-lockfile --verbose
    Updating registry `[https://github.com/rust-lang/crates.io-index`](https://github.com/rust-lang/crates.io-index%60)
error: no matching package named `actual-serde` found
location searched: registry `https://github.com/rust-lang/crates.io-index`
required by package `bitcoin v0.29.0`
    ... which is depended on by `bitcoincore-rpc-json v0.[16](https://github.com/rust-bitcoin/rust-bitcoincore-rpc/runs/7736593860?check_suite_focus=true#step:4:17).0 (file:///home/runner/work/rust-bitcoincore-rpc/rust-bitcoincore-rpc/json)`

Actual serde?

[tcharding]

Ha! Took me a while to decipher that error, then I noticed I did that already, its in the first line of the PR description:

This update breaks MSRV 1.29 so cannot be merged until we merge: #222

[stevenroose]

Can be rebased now that #222 is in.

[tcharding]

Rebase only, no other changes.

[DanGould]

tACK e6f334f 👍

[tcharding]

Can we have a release as well please? CC @stevenroose