Re-use bitcoin crate exported by gl-client

[ok300]

This PR removes the explicit dependency on bitcoin in our Cargo.toml. Instead of it, we use the version re-exported by GL at gl_client::bitcoin.

This helps us avoid having to track and re-align the bitcoin version with each gl_client update.

[JssDWt]

When is this an issue? When gl_client updates their bitcoin version? Only on minor version upgrades, or any upgrade? Looks like this here contains a downgrade of the bitcoin crate? #777

[ok300]

When is this an issue? When gl_client updates their bitcoin version? Only on minor version upgrades, or any upgrade?

There are different uses for the bitcoin crate:

• sometimes we use it directly
• sometimes we use structs from the bitcoin crate of other dependencies (i.e. its a transitive dependency), so there rust will choose the right version
• sometimes, things can be serialized with one version, then deserialized with another, which can be tricky to spot

My goal here is to reduce these possible combinations. If we use GL's version, the matrix of combinations has one less row.

Looks like this here contains a downgrade of the bitcoin crate? #777

GL is internally using 3 different bitcoin versions, each coming from different dependencies. I don't know if they upgrade or downgrade, but IMO GL is the most important dependency we have, so its best if we align with the version they use. This PR does that automatically.

[JssDWt]

LGTM, but madness that this is necessary ofcourse.