Switch alloy support from linera_alloy to alloy. (linera-io#3087)

## Motivation

We introduced the `linera_alloy` when we needed a version of `alloy`
from crates.io
In the meantime, `alloy` has been fully published in crates.io
Therefore, we switch to this version.

## Proposal

We switch from `linera_alloy` to `alloy` version 0.9.2 (the latest one)
in the crates.io
We also remove the `get_wallet` which is not used.

## Test Plan

The CI does the testing.

## Release Plan

This is currently not being used in the TestNet / DevNet, so it does not
really matter.

## Links

None

Cargo.toml

@@ -100,7 +100,8 @@ gloo-utils = "0.2.0"
 indexed_db_futures = "0.4.1"
 insta = "1.36.1"
 is-terminal = "0.4.12"
-linera-alloy = { version = "0.1.0", default-features = false }
+alloy = { version = "0.9.2", default-features = false }
+alloy-signer-local = "0.9.2"
 log = "0.4.21"
 lru = "0.12.3"
 linked-hash-map = "0.5.6"