fix: don't bake COMPILATION_MODE into launcher as exported environment var

This approach is incorrect as tools that are build for host such as "rollup_bin" in the rollup_bundle rule will see the --host_compilation_mode and not the --compilation_mode configuration value when built by Bazel as their cfg in the rule is correctly set to "host".

```
    "rollup_bin": attr.label(
        doc = "Target that executes the rollup binary",
        executable = True,
        cfg = "host",
        default = "@npm//rollup/bin:rollup",
    ),
```

The correct approach is to pass COMPILATION_MODE via the actions.run env attribute.

For the rollup_bundle rollup_bin tool, this is passed via run_node:

```
def run_node(ctx, inputs, arguments, executable, **kwargs):
    """Helper to replace ctx.actions.run
    This calls node programs with a node_modules directory in place"""
    ....
    # Forward the COMPILATION_MODE to node process as an environment variable
    env = kwargs.pop("env", {})
    if "COMPILATION_MODE" not in env.keys():
        env["COMPILATION_MODE"] = ctx.var["COMPILATION_MODE"]

    ctx.actions.run(
        inputs = inputs + extra_inputs,
        arguments = arguments,
        executable = exec_exec,
        env = env,
        **kwargs
    )
```

for other tools such the terser_minified terser_bin tool, this is done directly in ctx.actions.run:

```
    ctx.actions.run(
        inputs = inputs,
        outputs = outputs,
        executable = ctx.executable.terser_bin,
        arguments = [args],
        env = {"COMPILATION_MODE": ctx.var["COMPILATION_MODE"]},
        progress_message = "Minifying JavaScript %s [terser]" % (outputs[0].short_path),
    )
```

Accordingly `COMPILATION_MODE` is removed from default_env_vars so it is not baked into the launcher.sh.

`DEBUG` is also removed as a DEBUG define should not be default be passed to all nodejs_binary targets as it may unexpectantly affect the build outputs and if you do want to pass --define=DEBUG=1 to a tool such as the bazel_integration_test test_runner.js, also forwarding it to all nodejs_binaries will result in a massive
cache invalidation.