feat: Add `Deno.exitCode` API (#23609)

This commits adds the ability to set a would-be exit code 
for the Deno process without forcing an immediate exit, 
through the new `Deno.exitCode` API.

- **Implements `Deno.exitCode` getter and setter**: Adds support for
setting
and retrieving a would-be exit code via `Deno.exitCode`.
This allows for asynchronous cleanup before process termination 
without immediately exiting.
- **Ensures type safety**: The setter for `Deno.exitCode` validates that
the provided value is a number, throwing a TypeError if not, to ensure
that
only valid exit codes are set.

Closes to #23605

---------

Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>

3 files changed, 25 insertions, 0 deletions

diff --git a/tests/specs/test/exit_code/__test__.jsonc b/tests/specs/test/exit_code/__test__.jsonc
new file mode 100644
index 000000000..37d678453
--- /dev/null
+++ b/tests/specs/test/exit_code/__test__.jsonc
@@ -0,0 +1,5 @@
+{
+  "args": "test main.js",
+  "exitCode": 1,
+  "output": "main.out"
+}
diff --git a/tests/specs/test/exit_code/main.js b/tests/specs/test/exit_code/main.js
new file mode 100644
index 000000000..768bb4165
--- /dev/null
+++ b/tests/specs/test/exit_code/main.js
@@ -0,0 +1,3 @@
+Deno.test("Deno.exitCode", () => {
+  Deno.exitCode = 42;
+});
diff --git a/tests/specs/test/exit_code/main.out b/tests/specs/test/exit_code/main.out
new file mode 100644
index 000000000..2562695a0
--- /dev/null
+++ b/tests/specs/test/exit_code/main.out
@@ -0,0 +1,17 @@
+running 1 test from ./main.js
+Deno.exitCode ... FAILED ([WILDCARD])
+
+ ERRORS 
+
+Deno.exitCode => ./main.js:1:6
+error: Error: Test case finished with exit code set to 42.
+    at exitSanitizer (ext:cli/40_test.js:113:15)
+    at async outerWrapped (ext:cli/40_test.js:134:14)
+
+ FAILURES 
+
+Deno.exitCode => ./main.js:1:6
+
+FAILED | 0 passed | 1 failed ([WILDCARD])
+
+error: Test failed