This allows users to configure the maximum length of a single line
`let-else` statements. `let-else` statements that otherwise meet the
requirements to be formatted on a single line will have their divergent
`else` block formatted over multiple lines if they exceed this length.
**Note**: `single_line_let_else_max_widt` will be introduced as a stable
configuration option.
These test cases try to cover various edge cases. For example, comments
around the else keyword and long, unbreakable, single-line initializer
expressions, and long patterns.
The function properly handles recovering comments before and after the
`else` keyword, and properly handles how to write the else when users
configure `control_brace_style`.
