Add --force-interactive arg to prompt password

[gedex]

With SVN >= 1.8, an error is thrown when attempting to run wpt release:wporg:

Error: svn: E215004: Authentication failed and interactive prompting is disabled; see the --force-interactive option
svn: E215004: Commit failed (details follow):
svn: E215004: No more credentials or we tried too many times.
Authentication failed

From this changeset, SVN is non-interactive by default. Before that, it'll prompt password and cache it. Now the option is either makes it non-interactive and introduces --password as a mandatory arg, or pass --force-interactive in svn commit.

The first option is not ideal as it would be cumbersome to type it on every deploy. It's possible to read from env var where the password is stored. The last option is easier and much preferred as it behaves similarly in which it remembers the password.