[PM-7014] Track MessagePack fork and turn off CI / recurring workflows (#3456)

* Remove messagepack submodule

* Migrate MessagePack fork to this repo

* Disable build CI

* Disable Renovate

* Disable Crowdin recurring job

* Address workflow linter errors

lib/MessagePack/MessagePack-FlightSchool.podspec

@@ -0,0 +1,32 @@
+Pod::Spec.new do |s|
+    s.name = 'MessagePack-FlightSchool'
+    s.module_name  = 'MessagePack'
+    s.version      = '1.2.4'
+    s.summary      = 'A MessagePack encoder and decoder for Codable types.'
+
+    s.description  = <<-DESC
+      This functionality is discussed in Chapter 7 of
+      Flight School Guide to Swift Codable.
+    DESC
+
+    s.homepage     = 'https://flight.school/books/codable/'
+
+    s.license      = { type: 'MIT', file: 'LICENSE.md' }
+
+    s.author = { 'Mattt' => 'mattt@flight.school' }
+
+    s.social_media_url   = 'https://twitter.com/mattt'
+
+    s.ios.deployment_target = '8.0'
+    s.osx.deployment_target = '10.10'
+    s.watchos.deployment_target = '2.0'
+    s.tvos.deployment_target = '9.0'
+
+    s.source = { git: 'https://github.com/Flight-School/MessagePack.git',
+                 tag: s.version.to_s }
+
+    s.source_files = 'Sources/**/*.swift'
+
+    s.swift_version = '4.2'
+    s.static_framework = true
+end