Add sqlite module

[notmandatory]

In addition to adding sqlite support I also added some instructions in the README for how to run the tests locally.

This is mainly a copy/paste of the postgres module with minor changes required to work with sqlite. At some point we could probably remove some of the duplication. But for now this works well enough for me to use in my TABConf workshop. 🙂

[notmandatory]

I changed all the tests to 1. run with both the postgres and sqlite stores, 2. drop the postgres tables at the start of each test instead of the end, this makes it possible to debug what is in the DB if a test fails, 3. removed duplicate store setup code and put it all in a new create_test_stores().

[ValuedMammal]

The postgres example will be easier to run if we have an [[example]] section in Cargo.toml and just have a file examples/bdk_sqlx_postgres.rs without the extra Cargo.toml. Or we can turn the project into a workspace with multiple crates like the bdk repo but that will be more work. Right now the example looks like a crate inside of a crate which is causing rust-analyzer to complain that it's an "unlinked file"

[notmandatory]

@ValuedMammal thanks for the [[example]] suggestion, I should have looked up the right way to do it, fixed.

[ValuedMammal]

This looks good to me, all tests passing. Not sure if there's any remaining comments from @matthiasdebernardini before merging

[ValuedMammal]

I didn't find an easy way to call this from outside the library, I guess because the module is private?

[notmandatory]

I think we should remove these functions since they only print to stdout they belong in an example or new function on Store that returns list of wallet names. But can do that in a separate PR this one is already pretty big.

[matthiasdebernardini]

Do we want to test trying to store a private key and make sure it only stores the public key? If not let's get this merged in, I still need to figure out how to make the migrations run without an external sql file. I also need to look into schemas so that these tables are segregated from the rest of the application.

[notmandatory]

I don't think we need any new tests in this crate to confirm only pubkey descriptors are stored, those belong in the wallet persister tests.