Consolidate GitHub CI actions, split out Monero (#71)

* Consolidate GitHub CI actions, split out Monero

build now includes the specified Rust toolchain/components.

Added a test dependencies action which grabs Foundry and Monero.

Split the Monero v14 job into a matrixed job in its own workflow flow. 
It's now only run when Monero has changes.

* Correct Monero unit/integration tests run timing

Additionally tests a feature-less Monero build.

Also removes a pointless Monero file, which already should have been 
removed, causing this workflow to be triggered.

* Correct exclusion and paths

Updates to FROST should re-run the Monero tests to ensure it didn't 
introduce API incompatibilities.

.github/actions/test-dependencies/action.yml

@@ -0,0 +1,24 @@
+name: test-dependencies
+description: Installs test dependencies for Serai
+
+inputs:
+  monero-version:
+    description: "Monero version to download and run as a regtest node"
+    required: false
+    default: v0.18.0.0
+
+runs:
+  using: "composite"
+  steps:
+    - name: Install Build Dependencies
+      uses: ./.github/actions/build-dependencies
+
+    - name: Install Foundry
+      uses: foundry-rs/foundry-toolchain@v1
+      with:
+        version: nightly
+
+    - name: Run a Monero Regtest Node
+      uses: ./.github/actions/monero
+      with:
+        version: ${{ inputs.monero-version }}