Before, "jj config get"/"list" and .get() functions processed inline tables as
tables (or directories in filesystem analogy), whereas "set"/"unset" processed
ones as values (or files.) This patch makes all commands and functions process
inline tables as values. We rarely use the inline table syntax, and it's very
hard to pack many (unrelated) values into an inline table. TOML doesn't allow
newlines between { .. }. Our common use case is to define color styles, which
wouldn't be meant to inherit attributes from the default settings.

The default pager setting is flattened in case user overrides pager.env without
changing the command args.