feat: support experimental doc entries
- Params/options/members are marked as experimental in the docs.
- `experimental.d.ts` is generated that contains all types and
includes experimental features.
- `experimental.d.ts` is references in our tests so that we
can test experimental features.
- `fonts` option is restored as experimental.
- Always show a fixture that was running during timeout.
- Give custom titles to built-in fixtures.
- Specify setup/teardown fixture phase in the message.
- Split connect vs launch browser fixtures for better naming.
Example timeout message:
```log
Timeout of 2000ms exceeded while running fixture "built-in playwright configuration" teardown.
```
Reason: turns out Debian Buster requires just one source list to
install `ttf-ubuntu-font-family` font.
All other dependencies are satisfied.
Fixes#13530
Firefox has a bug: calling `node.focus()` does make the node focused,
but some internal "current contenteditable node" is not changed.
Blurring the previous one and focusing the new one helps.
To make launch/connect not affect the test timeout:
- `browser` fixture is declared with `timeout: 0`.
- Default timeouts are set to 30sec for launch and 3min for connect.
This was introduced in #7500 to fight `ERROR: The process "4436" not found.`
messages when killing a process that did already exit.
Since then, we no longer inherit stdout/stderr, so the error message
should not appear anymore.
This is a speculative fix to leftover tmp directories.
When users issues SIGINT twice, we enter `gracefullyClose()`
twice, and shortcut the second time. It turns out, we do
not wait for directories removal.
Note: it is unknown how often we reach this codepath in practice.
Previously, we were guessing whether something is optional from the
comment (looking for stuff like "defaults to" or "optional").
To remove this error-prone technique, every optional property or
argument (but not option) is explicitly marked with "?".
As a result, fix documentation issues:
- Removed `TestStep.data` that is not a thing.
- Added `TestConfig.name` documentation.
- Refined a lot of optional types in the documentation.
- Aligned `test.fail()` and `test.slow()` docs with `test.skip()`.
- Strict set of docs vs types inconsistensies in the generator
