Allow github release to be explicitly set as latest or explicitly not be latest

[mrgrain]

gh release create has three different modes for "latest":

• default; not specified - the latest release will be determined by date and version (see https://cli.github.com/manual/gh_release_create)
• --latest - this release will be set as the latest release
• --latest=false - this release will NOT be set as the latest release (see https://github.com/cli/cli/issues/6963)

projen currently only allows the default behavior.

We should change Publisher to accept all 3 variations of it. We should then expose this option via the Release component and releaseBranches.

---

Use case: I have a package with multiple release branches for older, but still supported versions. Currently releases for these older versions are still marked as "Latest" whenever they occur, despite them definitely not being the latest or recommend version to use.