Since 808bd4af4, we are no longer pre-verifying PRs before uploading the build
artifacts to the preview server, thus we no longer need the
`travis-preverify-pr.sh` script or the `GITHUB_TEAM_MEMBERSHIP_CHECK_KEY`
variable.
There have been some issues lately with Travis jobs failing due to
`print-log.sh`. This is likely due to trying to print the Lighthouse PWA report,
which is too large.
This commit stops printing that report (since it was rarely used and is pretty
easy to acquire when needed) and restores the `print-logs.sh` script (that was
temporarily removed with dfcca66fd).
The current stable branch is determined based on the current version mapped to
the npm `latest` tag (by replacing the patch version number with 'x' - e.g.
`1.2.3` --> `1.2.x`).
PRs against the stable branch will be deployed to the preview server (as long as
the rest of the requirements are met). Commits on the stable branch itself will
be deployed to production.
Fixes#16908
Gaining access to another PR's JWT, would allow faking that PR's author wrt to
GitHub team membership verification for as long as the JWT is valid (currently
90 mins).