Update min Swift version to 5.6 and make platform versions consistent (#205)

Update minimum Swift version to 5.6 and make platform versions consistent.

Author: gwynne

.github/workflows/test.yml

@@ -71,7 +71,7 @@ jobs:
   api-breakage:
     if: github.event_name == 'pull_request'
     runs-on: ubuntu-latest
-    container: swift:5.7-jammy
+    container: swift:5.8-jammy
     steps:
       - name: Check out package
         uses: actions/checkout@v3
@@ -85,10 +85,10 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - {dbimage: 'postgres:11', dbauth: 'trust',         swiftver: 'swift:5.5-bionic'}
-          - {dbimage: 'postgres:13', dbauth: 'md5',           swiftver: 'swift:5.6-focal'}
-          - {dbimage: 'postgres:15', dbauth: 'scram-sha-256', swiftver: 'swift:5.7-jammy'}
-          - {dbimage: 'postgres:15', dbauth: 'scram-sha-256', swiftver: 'swiftlang/swift:nightly-5.8-jammy'}
+          - {dbimage: 'postgres:11', dbauth: 'trust',         swiftver: 'swift:5.6-focal'}
+          - {dbimage: 'postgres:13', dbauth: 'md5',           swiftver: 'swift:5.7-jammy'}
+          - {dbimage: 'postgres:15', dbauth: 'scram-sha-256', swiftver: 'swift:5.8-jammy'}
+          - {dbimage: 'postgres:15', dbauth: 'scram-sha-256', swiftver: 'swiftlang/swift:nightly-5.9-jammy'}
           - {dbimage: 'postgres:15', dbauth: 'scram-sha-256', swiftver: 'swiftlang/swift:nightly-main-jammy'}
     container: ${{ matrix.swiftver }}
     runs-on: ubuntu-latest
@@ -163,6 +163,7 @@ jobs:
   test-exports:
     name: Test exports
     runs-on: ubuntu-latest
+    container: swift:5.8-jammy
     steps:
       - name: Check out Vapor
         uses: actions/checkout@v3

Package.swift

@@ -1,12 +1,13 @@
-// swift-tools-version:5.5.2
+// swift-tools-version:5.6
 import PackageDescription
 
 let package = Package(
     name: "fluent-postgres-driver",
     platforms: [
         .macOS(.v10_15),
         .iOS(.v13),
-        .watchOS(.v6)
+        .watchOS(.v6),
+        .tvOS(.v13),
     ],
     products: [
         .library(name: "FluentPostgresDriver", targets: ["FluentPostgresDriver"]),