sequencer: fix flaky unit tests

[noot]

the tests are flaky due to using a global for the native asset:

failures:

error: test failed, to rerun pass `-p astria-sequencer --lib`
---- app::test::app_deliver_tx_bridge_lock_action_invalid_for_eoa stdout ----
thread 'app::test::app_deliver_tx_bridge_lock_action_invalid_for_eoa' panicked at crates/astria-sequencer/src/asset/mod.rs:18:10:
native asset should only be set once: Denom { id: Id([112, 64, 49, 200, 104, 253, 61, 60, 132, 161, 207, 168, 203, 69, 222, 186, 78, 167, 70, 180, 70, 151, 247, 244, 166, 237, 27, 143, 108, 35, 155, 130]), base_denom: "nria", prefix: "" }
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace


failures:
    app::test::app_deliver_tx_bridge_lock_action_invalid_for_eoa

potential solutions from @SuperFluffy :

• Remember the const-sha2 impl that I made in March 2023? (And was ultimately of no use to us)? We could bake that into our services, since that's what your denom id is basically make it work on stable saleemrashid/sha2-const#5
• You move the global initializer outside the squencer library-initializer and into main. So basically you make a freestanding function that you call from main. The accessors in the library-part of Sequencer never initialize, only access. This way you can protect the global similar to how we do telemetry bringup
• Another option is function memoization which is a more batteries-included (but similar approach) to oncecell/lazy etc

[noot]

closing for now as i have not seen any flakiness in a while