Drop support for Swift 6.0 (#908)

Motivation:

Swift 6.0 has dropped out of the support policy

Modifications:

- Remove Package@swift-6.0.swift
- Ensure min tools version is 6.1

Result:

AHC only supports Swift 6.1+

Author: glbrntt

.github/workflows/pull_request.yml

@@ -17,8 +17,6 @@ jobs:
         name: Unit tests
         uses: apple/swift-nio/.github/workflows/unit_tests.yml@main
         with:
-            linux_5_10_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors"
-            linux_6_0_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors"
             linux_6_1_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors"
             linux_6_2_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors"
             linux_nightly_next_arguments_override: "--explicit-target-dependency-import-check error"
@@ -27,8 +25,6 @@ jobs:
     cxx-interop:
         name: Cxx interop
         uses: apple/swift-nio/.github/workflows/cxx_interop.yml@main
-        with:
-            linux_5_9_enabled: false
 
     static-sdk:
         name: Static SDK

Package@swift-6.0.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:6.0
+// swift-tools-version:6.1
 //===----------------------------------------------------------------------===//
 //
 // This source file is part of the AsyncHTTPClient open source project

Package@swift-6.1.swift

@@ -306,7 +306,7 @@ Please have a look at [SECURITY.md](SECURITY.md) for AsyncHTTPClient's security
 
 ## Supported Versions
 
-The most recent versions of AsyncHTTPClient support Swift 6.0 and newer. The minimum Swift version supported by AsyncHTTPClient releases are detailed below:
+The most recent versions of AsyncHTTPClient support Swift 6.1 and newer. The minimum Swift version supported by AsyncHTTPClient releases are detailed below:
 
 AsyncHTTPClient     | Minimum Swift Version
 --------------------|----------------------
@@ -319,4 +319,5 @@ AsyncHTTPClient     | Minimum Swift Version
 `1.21.0 ..< 1.26.0` | 5.8
 `1.26.0 ..< 1.27.0` | 5.9
 `1.27.0 ..< 1.30.0` | 5.10
-`1.30.0 ...`        | 6.0
+`1.30.0 ..< 1.34.0` | 6.0
+`1.34.0 ...`        | 6.1

README.md

@@ -47,11 +47,7 @@ final class HTTPClientTests: XCTestCaseHTTPClientTestsBaseClass {
 
         let request3 = try Request(url: "unix:///tmp/file")
         XCTAssertEqual(request3.host, "")
-        #if os(Linux) && compiler(<6.1)
-        XCTAssertEqual(request3.url.host, "")
-        #else
         XCTAssertNil(request3.url.host)
-        #endif
         XCTAssertEqual(request3.url.path, "/tmp/file")
         XCTAssertEqual(request3.port, 80)
         XCTAssertFalse(request3.useTLS)