Fixes#4603.
Tests explain it the best:
```js
describe('development mode (no chunkhash)', () => {
it('should strip the extension from the filename', () => {
const filename = 'foo_bar_0123456789abcdef.js'
expect(getChunkNameFromFilename(filename, true)).toBe('foo_bar_0123456789abcdef')
})
it('should only strip the extension even if there\'s a hyphen in the name', () => {
const filename = 'foo-bar-0123456789abcdef.js'
expect(getChunkNameFromFilename(filename, true)).toBe('foo-bar-0123456789abcdef')
})
})
describe('production mode (with chunkhash)', () => {
it('should strip the hash from the filename', () => {
const filename = 'foo_bar_0123456789abcdef-0123456789abcdef.js'
expect(getChunkNameFromFilename(filename, false)).toBe('foo_bar_0123456789abcdef')
})
it('should only strip the part after the last hyphen in the filename', () => {
const filename = 'foo-bar-0123456789abcdef-0123456789abcdef.js'
expect(getChunkNameFromFilename(filename, false)).toBe('foo-bar-0123456789abcdef')
})
})
```
This fixes a missed bug introduced in #4510.
Because the regexp was `/-[^-]*/` and not `/-[^-]*$/`, a wrong part of the filename was being removed:
```
bad:
'foo-bar-0123456789abcdef-0123456789abcdef.js' -> 'foo-0123456789abcdef-0123456789abcdef.js'
good:
'foo-bar-0123456789abcdef-0123456789abcdef.js' -> 'foo-bar-0123456789abcdef'
```
By a stroke of luck this didn't affect the existing dynamically generated chunks. To prevent regression I've added unit tests for the function that generates the name.
Btw. in the original issue (#4433) I used the right regexp, I just used the wrong regexp in #4510.
cc @timneutkens
