Support generating release notes

[caithagoras]

The PR introduces a tool which formalize the release notes collection in the release process.

Release Notes Collection

To streamline the release process, we introduced a requirement (and PR template) to ask authors to write release notes in the PR description. During the release process, the person doing the release will be able to use this tool to collect and generate the release commit and PR, before polishing it as according to the Release Notes Guideline.

What does the tool do

1. Switch to master branch. Fast-forward to upstream master.
2. Use git log to find the commits introduced in the new release.
3. Use Github GraphQL API v4 to fetch the PRs associated with the commits.
4. Parse the PR description, generate release notes, create release branch, modify local files, create release notes commit, and push to origin.
5. Create a release notes PR, with description populated. Release notes PR description contains 3 sections:
   a. A list of PRs with missing release notes, either the PR description do not contain release notes, or the release notes were malformed.
   b. A list of extracted release notes.
   c. A list of all commits introduced in the release.

How to use the tool

To collect release notes, run the following command after cutting the release branch (bumping the snapshot version on the master branch):

curl -L -o /tmp/presto_release "https://oss.sonatype.org/service/local/artifact/maven/redirect?g=com.facebook.presto&a=presto-release&v=LATEST&r=snapshots&c=executable&e=jar"
chmod 755 /tmp/presto_release
/tmp/presto_release release-notes --github-user <GITHUB_USER> --github-access-token <GITHUB_ACCESS_TOKEN>

[caithagoras]

Supersedes prestodb/presto#13964

[caithagoras]

@aweisberg Addressed all comments in prestodb/presto#13964

[mayankgarg1990]

LGTM

[caithagoras]

• Move .travis.yml to the first commit
• Made a few fixes, will squash before merging