Glean-parser

- BUGFIX: Fix rendering of first element of reason list.

- BUGFIX: Reason codes are displayed in markdown output for built-in
pings as well.
- BUGFIX: Reason descriptions are indented correctly in markdown
output.
- BUGFIX: To avoid a compiler error, the `JvmName` annotation isn't
added to private members.

- **Breaking Change (Java API)** Have the metrics names in Java match the names
in Kotlin. See [Bug
1588060](https://bugzilla.mozilla.org/show_bug.cgi?id=1588060).
- The reasons a ping are sent are now included in the generated markdown
documentation.

- BUGFIX: The version of Jinja2 now specifies < 3.0, since that version no
longer supports Python 3.5.

- BUGFIX: Fixes an import error in generated Kotlin code.

- BUGFIX: Generated Swift code now includes `import Glean`, unless generating
for a Glean-internal build.