chore: Allow OS to assign port for unit tests

Previously we started looking for testing ports starting at 5000. If the
port was in use, we would incrementally search upwards until we found a
port we could use.

A recent change in the GH Windows image resulted in a permission error
being raised before we could find a port to use:

```
Failure/Error: WEBrick::HTTPServer.new(base_opts)

Errno::EACCES:
Permission denied - bind(2) for 127.0.0.1:50018
```

To address this, we are modifying the tests to set a port of 0, which
will allow the OS to assign an available port for us. This removes the
need for this silly retry logic and hard coded port numbers.

Author: keelerm84

.github/workflows/ci.yml

@@ -13,6 +13,7 @@ jobs:
   build-linux:
     uses: ./.github/workflows/build-gem.yml
     strategy:
+      fail-fast: false
       matrix:
         version: ["3.2", "jruby-9.4"]
     with:

spec/http_util.rb

@@ -7,36 +7,25 @@
 class StubHTTPServer
   attr_reader :requests, :port
 
-  @@next_port = 50000
-
   def initialize(enable_compression: false)
-    @port = StubHTTPServer.next_port
     @enable_compression = enable_compression
-    begin
-      base_opts = {
-        BindAddress: '127.0.0.1',
-        Port: @port,
-        AccessLog: [],
-        Logger: NullLogger.new,
-        RequestCallback: method(:record_request),
-      }
-      @server = create_server(@port, base_opts)
-    rescue Errno::EADDRINUSE
-      @port = StubHTTPServer.next_port
-      retry
-    end
+    base_opts = {
+      BindAddress: '127.0.0.1',
+      Port: 0,  # Let OS assign an available port
+      AccessLog: [],
+      Logger: NullLogger.new,
+      RequestCallback: method(:record_request),
+    }
+    @server = create_server(base_opts)
     @requests = []
     @requests_queue = Queue.new
   end
 
-  def self.next_port
-    p = @@next_port
-    @@next_port = (p + 1 < 60000) ? p + 1 : 50000
-    p
-  end
-
-  def create_server(port, base_opts)
-    WEBrick::HTTPServer.new(base_opts)
+  def create_server(base_opts)
+    server = WEBrick::HTTPServer.new(base_opts)
+    # Get the actual port assigned by the OS
+    @port = server.config[:Port]
+    server
   end
 
   def start