feat(cli): Add slow test warning (#23874)

By default, uses a 60 second timeout, backing off 2x each time (can be
overridden using the hidden `DENO_SLOW_TEST_TIMEOUT` which we implement
only really for spec testing.

```
Deno.test(async function test() {
  await new Promise(r => setTimeout(r, 130_000));
});
```

```
$ target/debug/deno test /tmp/test_slow.ts 
Check file:///tmp/test_slow.ts
running 1 test from ../../../../../../tmp/test_slow.ts
test ...'test' is running very slowly (1m0s)
'test' is running very slowly (2m0s)
 ok (2m10s)

ok | 1 passed | 0 failed (2m10s)
```

---------

Signed-off-by: Matt Mastracci <matthew@mastracci.com>
Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>

0 files changed, 0 insertions, 0 deletions