Migrate tests to typescript with `ts-jest`

Test cases are written in javascript and it depends on dist, which causes 3 issues:

1. coverage data is not clear for each module, only shows sval.js
2. need to run start, before running test, and it’s easy to forget to run start script.
3. no intellisense support when writing test cases.

I will give a PR later.

[bloody-ux]

try it. but I still would like to use ts-jest, and I will find some way to fix issue 2. umi-test is based on jest and enzyme, so I think the problem will be still there.

umi-test can resolve the issue, I just tested and have a new PR. because it uses babel-jest instead of ts-jest

[bloody-ux]

issue 1 can be resolved with this pr