build: unbundle pester (#5623)

* remove pester module

* restore Pester as a module only in CI build from the git repo

* mark appveyor builds as CI builds

* remove pester exclusions

* mark travis builds as ci

* exclude publish folder from spell check

* do not run spell check on publish folder

.gitmodules

@@ -1,8 +1,3 @@
-[submodule "src/Modules/Pester"]
-	path = src/Modules/Shared/Pester
-	url = https://github.com/PowerShell/psl-pester.git
-	branch = develop
-	ignore = dirty
 [submodule "src/libpsl-native/test/googletest"]
 	path = src/libpsl-native/test/googletest
 	url = https://github.com/google/googletest.git