[js/common] add unit tests for onnxruntime-common (#16812)
### Description
"onnxruntime-common" starts to get more and more complicated, so it's a
good idea to add unit tests for it.
Includes the following changes:
- move `mocha` from each subfolder (js/web/, js/node/) to root (js/), so
that it will be installed once and all subfolder can use.
- add folder `test` in js/common/ as root folder for ort-common tests.
- add sub folder `type-tests`. this folder contains a few typescript
source code, which are excluded from the tsconfig.json. they are not
compiled by default. instead, file `type-tests.ts` calls typescript
compiler (tsc) to check for the files under this folder whether the
compilation result is as expected. If tsc compiles a file successfully
when a failure is expected, this is considered an failed test.
- add sub folder `unit-tests`. files under this folder will be compiled
by default. we use default mode of mocha (using `describe()` and `it()`)
to setup test groups and cases.
- update eslint rules accordingly.
