Fix transaction passthrough types, and add linting for examples

[dcousens]

#9280 introduced prismaTypes to .keystone/types, but Prisma is a namespace, not a type.

I don't have the capacity to fix this canonically right now, thus I have inlined the isolationLevel type, and added a target for CI tests to catch this in future.

../auth/node_modules/.keystone/types.ts:172:40 - error TS2694: Namespace '"/home/keystone/workspace/keystone/examples/auth/node_modules/myprisma/index"' has no exported member 'Prisma'.

172   prismaTypes: import('./../myprisma').Prisma
                                           ~~~~~~

Found 53 errors in 53 files.

Errors  Files
     ...
     1  ../auth/node_modules/.keystone/types.ts:137
     ...

@acburdine if you wanted to follow this up with a fix, I'm happy to revert this 💛