Add development script and commands

[thunderbiscuit]

This PR adds new "development" workflows for compiling the libraries quickly when developing locally.

In bdk-android, you can run the new dev-macos.sh script by using just build-dev. It will compile the library for a single architecture, the one I currently use.

In bdk-ffi, you can run cargo build (which builds the faster but unoptimized version of the library) using just build-dev.

In Swift, I'd be great to add at least one similar script to build the faster version of the library for local testing. @reez let me know what that would look like (or feel free to push a commit to this PR).

Documentation

No docs to add.

• [ ] bdk_wallet
• [ ] bitcoin
• [ ] uniffi
• [ ] Other:

Checklists

All Submissions:

• [x] I've signed all my commits
• [x] I followed the contribution guidelines