### Motivation:

Useful for parsing packets, for example `ipv4: InlineArray<4, UInt8>`
and `ipv6: InlineArray<16, UInt8>`.

### Modifications:

For now I've only added a `readInlineArray` function. I know some other
functions are missing, such as `writeInlineArray`.
I wanted to first open up a discussion and see if these changes are
acceptable. I can add those functions too if required, in this PR or
other PRs.

### Result:

Users can read `ByteBuffer` into stack-allocated memory, which can be
more performant than the other alternatives like `Array`, or more
convenient than reading as a tuple like `(UInt8, UInt8, UInt8, UInt8)`.

### Caveats:

Swift 6.2 is required so I've used `#if compiler(>=6.2)`.
Furthermore, `InlineArray` is marked as available on `macOS(9999)` since
the Swift team have yet to update that mark, although `InlineArray` is
planned for Swift 6.2 per the
[proposal](https://github.com/swiftlang/swift-evolution/blob/main/proposals/0453-vector.md).

Edit: to be clear things work fine on Linux and that's where I've been
using this same `readInlineArray` function that I've proposed.

---------

Co-authored-by: Cory Benfield <lukasa@apple.com>

…3387)

See #3386
CC @FranzBusch @ktoso @Lukasa

Signed-off-by: Melissa Kilby <mkilby@apple.com>

…3389)

See #3386
CC @FranzBusch @ktoso @Lukasa

Signed-off-by: Melissa Kilby <mkilby@apple.com>
Co-authored-by: Rick Newton-Rogers <rnro@apple.com>

#3390)

See #3386
CC @FranzBusch @ktoso @Lukasa

Signed-off-by: Melissa Kilby <mkilby@apple.com>

#3391)

See #3386
CC @FranzBusch @ktoso @Lukasa

Signed-off-by: Melissa Kilby <mkilby@apple.com>

…3388)

See #3386
CC @FranzBusch @ktoso @Lukasa

Signed-off-by: Melissa Kilby <mkilby@apple.com>
Co-authored-by: Rick Newton-Rogers <rnro@apple.com>

Motivation

Availability guards on test functions don't work the way we'd want them
to: in particular, xctest still ends up calling these functions even on
platforms that are less available than the functions in question. We
need to move these to checks in in the function themselves.

Modifications

Replace @available with guard available

Result

No more segfaults in tests.

This PR drops Swift 5.10 and enables Swift 6 language mode.

---------

Co-authored-by: Cory Benfield <lukasa@apple.com>

Motivation:

This test occasionally fails in our ongoing continuous CI solution.
Flaky tests are bad, and we should aim not to have them, so let's fix
it.

My diagnosis of the most likely race here (which leads to
`alreadyClosed`) being thrown _somewhere_ from this code is that the
client channel got closed unexpectedly. This would happen if an unusual
series of events occurs:

1. The client connection succeeds and the channel starts up
2. The server close then goes through and the server channel is closed
_before_ it actually accepts the connection.
3. This causes the client connection to be reset.
4. The client channel observes this and handles that close.
5. We then close the client from the outside.

Modifications:

Add a ConditionLock we can use to wait for a connection to be
established.
Make the use of this ConditionLock resilient to weird test behaviour by
always using timeouts for blocking operations.

Result:

Less flaky tests.

…ws (#3396)

See #3386

Note: I consistently placed the permissions key at the top (slightly
corrected recent PRs).

CC @rnro

Signed-off-by: Melissa Kilby <mkilby@apple.com>

26.1 Beta 2 has been released so we have an Xcode beta to be testing, we
should enable it by default again. It was previously disabled under the
impression that there was no current beta.