Use cargo-nextest with retries for flaky LSP test (#6521)

## Description
This PR introduces [`cargo-nextest`](https://nexte.st/) to improve our
test runs. We've configured 2 retries for the go_to_definition_for_paths
test, which has been intermittently failing. The LSP CI workflow has
been updated to use `cargo-nextest`.

Should mitigate #6029 until we get to the root cause why these tests are
flaky.

## Checklist

- [x] I have linked to any relevant issues.
- [ ] I have commented my code, particularly in hard-to-understand
areas.
- [ ] I have updated the documentation where relevant (API docs, the
reference, and the Sway book).
- [ ] If my change requires substantial documentation changes, I have
[requested support from the DevRel
team](https://github.com/FuelLabs/devrel-requests/issues/new/choose)
- [ ] I have added tests that prove my fix is effective or that my
feature works.
- [ ] I have added (or requested a maintainer to add) the necessary
`Breaking*` or `New Feature` labels where relevant.
- [ ] I have done my best to ensure that my PR adheres to [the Fuel Labs
Code Review
Standards](https://github.com/FuelLabs/rfcs/blob/master/text/code-standards/external-contributors.md).
- [ ] I have requested a review from the relevant team or maintainers.

.github/workflows/ci.yml

@@ -541,15 +541,16 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
-      - name: Install toolchain
-        uses: dtolnay/rust-toolchain@master
+      - name: Setup Rust and cargo-nextest
+        uses: moonrepo/setup-rust@v0
         with:
-          toolchain: ${{ env.RUST_VERSION }}
-      - uses: Swatinem/rust-cache@v2
+          channel: stable
+          cache-target: release
+          bins: cargo-nextest
       - name: Run sway-lsp tests sequentially
         env:
           RUST_BACKTRACE: full
-        run: cargo test --locked --release -p sway-lsp -- --nocapture --test-threads=1
+        run: cargo nextest run --locked --release -p sway-lsp --no-capture --profile ci --config-file sway-lsp/tests/nextest.toml
   cargo-test-workspace:
     runs-on: ubuntu-latest
     steps:

sway-lsp/tests/lib.rs

@@ -973,7 +973,6 @@ fn go_to_definition_for_paths() {
         lsp::definition_check_with_req_offset(&server, &mut go_to, 7, 11).await;
         lsp::definition_check_with_req_offset(&server, &mut go_to, 7, 23).await;
 
-        // // TODO: This test stopped working when https://github.com/FuelLabs/sway/pull/6116 was merged.
         let mut go_to = GotoDefinition {
             req_uri: &uri,
             req_line: 22,

sway-lsp/tests/nextest.toml

@@ -0,0 +1,6 @@
+[profile.ci]
+retries = 0
+
+[[profile.ci.overrides]]
+filter = 'test(go_to_definition_for_paths)'
+retries = 2