Verifier: Check composite type template params

Add missing checks for `templateParams:` in `MDCompositeType`.  Pull the
current check for `MDSubprogram` to reduce duplicated code and fix it up
to print a good message when the immediate operand isn't an `MDTuple`
(as a drive-by, make the same fix to `variables:` in `MDSubprogram`).

llvm-svn: 234177