feat: implement baml-cli test (#1458)

NOT READY FOR MERGE YET: projected land date Feb 21

Design notes:


```bash
# past work
baml-cli test run --include "MyFunction::" --include "AnyMatch" --exclude "::LongTest"

# syntax: <part>::<part>
# syntax: "*\w\d_" for function/test filter clauses

baml-cli test list  # this is the default action because it costs $$$

baml-cli test run  # to run tests
baml-cli test --output-formats [pretty | github | junit=path/to/file.xml]
```

Product requirements:

- allow users to enforce that baml tests pass in CI
    - users may only want to run a subset of tests in CI
- filter based on file & name (in the future, maybe some kind of “test
tag” attribute)
        - `--include`
        - `--exclude`
        - tests for a given function
        - regex
    - `--verbose` - TBD
    - report timing stats - TBD
    - tests may be flakey and need re-running - TBD
- for github actions: we can use [[output
groups](https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/workflow-commands-for-github-actions#grouping-log-lines)](https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/workflow-commands-for-github-actions#grouping-log-lines)
    - for non-github aka generic integration (TBD) junit xml is a must
- cf [gitlab unit test
reports](https://docs.gitlab.com/ee/ci/testing/unit_test_reports.html)
- debug loop: what are users going to do when tests fail?
    - test failures need to show logs
    - re-run a specific test
        - can go into the wasm playground for this
- happy-ish path
- show # of tests that passed, timing info, # of tests skipped - take
`cargo test` as inspiration (maybe pytest/mocha too)
    - test execution will be concurrent
        - do we need concurrency limits?
- need to be able to set concurrency down to 1 (claude basic tier),
default concurrency should be... ???
        - definitely need timeouts too

Fixes #1345 
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----

> [!IMPORTANT]
> Adds `baml-cli test` command for running BAML tests with filtering,
output formats, and concurrency options, along with `.env` file support
and test execution integration with GitHub Actions and JUnit XML
reporting.
> 
>   - **CLI**:
> - Adds `baml-cli test` command in `commands.rs` to run BAML tests with
options for filtering (`--include`, `--exclude`), output formats
(`--output-format`), and concurrency (`--parallel`).
> - Integrates test execution with GitHub Actions and JUnit XML
reporting in `output_github.rs` and `output_junit.rs`.
>   - **Environment**:
> - Implements `.env` file loading in `dotenv/mod.rs` with support for
multiline strings, variable interpolation, and escape sequences.
>     - Adds tests for `.env` loading in `dotenv/tests.rs`.
>   - **Test Execution**:
> - Introduces `TestExecutor` trait in `test_executor/mod.rs` for
running tests with status tracking and rendering.
> - Implements `PrettyTestExecutionStatusRenderer`,
`GithubTestExecutionStatusRenderer`, and `JUnitXMLRenderer` for
different output formats.
> - Adds `TestFilter` in `test_execution_args.rs` for filtering tests
based on patterns.
> 
> <sup>This description was created by </sup>[<img alt="Ellipsis"
src="https://img.shields.io/badge/Ellipsis-blue?color=175173">](https://www.ellipsis.dev?ref=BoundaryML%2Fbaml&utm_source=github&utm_medium=referral)<sup>
for 01e78d6. It will automatically
update as commits are pushed.</sup>


<!-- ELLIPSIS_HIDDEN -->

---------

Co-authored-by: Vaibhav Gupta <vbv@boundaryml.com>

Author: sxlijin

.github/workflows/sandbox.yaml

@@ -0,0 +1,53 @@
+name: sandbox
+
+on:
+  push:
+    branches:
+      - sam/baml-test
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - name: bash output
+        run: |
+          # Start a log group.
+          echo "::group::Colored Log Group"
+
+          # Output text in various colors.
+          echo -e "::group::\033[31mThis is red text\033[0m"
+          echo -e "\033[32mThis is green text\033[0m"
+          echo "::endgroup::"
+          echo -e "\033[34mThis is blue text\033[0m"
+
+          # End the log group.
+          echo "::endgroup::"
+
+          echo -e "::group::\033[31mThis is red text\033[0m"
+          echo -e "\033[32mThis is green text\033[0m"
+          sleep 120
+          echo "::endgroup::"
+
+          # New log groups with pass/fail emojis
+          echo -e "::group::\033[32m✅ This is a pass message\033[0m"
+          echo "::endgroup::"
+
+          echo -e "::group::\033[31m❌ This is a fail message\033[0m"
+          echo "::endgroup::"
+
+          echo -e "::group::\033[32m✅ Another pass message\033[0m"
+          echo "::endgroup::"
+
+          echo -e "::group::\033[32m✅ Yet Another pass message\033[0m"
+          echo "sleep 120 start"
+          sleep 120
+          echo "sleep 120 done"
+          echo "::endgroup::"
+
+          # Output some colored text outside the group as well.
+          echo "Ungrouped colored output:"
+          echo -e "\033[35mThis is magenta text\033[0m"