feat: add option for disabling file downloads (#5055)

* feat(cli): add disable-file-downloads to cli

* feat(e2e): add download test

* feat(e2e): add downloads disabled test

* refactor(e2e): explain how to debug unexpected close

* feat(patches): add disable file downloads

* wip: update diff

* Update src/node/cli.ts

Co-authored-by: Asher <ash@coder.com>

* fixup! add missing common/contextkeys file to patch

* fixup!: update patch

* fixup!: default disable-file-downloads undefined

* fixup!: combine e2e tests

* fixup!: use different test names

* feat: add CS_DISABLE_FILE_DOWNLOADS

* fixup!: make explicit and cleanup test

* fixup!: use beforeEach

Co-authored-by: Asher <ash@coder.com>