This adds the `\` character to the list of characters which will
terminate matches in Alacritty's default hint for URL recognition.

This patch removes the `hold` option on `alacritty_terminal` in favor of
a `drain_on_exit` option, which will drain the PTY before shutdown. The
hold logic is instead handled in `alacritty`.

This fixes an issue with hints where it was possible that the terminal
content of highlighted hints changed between the highlighted hint update
and the activation of the hint.

This patch always validates the hint's text content against the hint
itself to ensure that the content is still valid for the original hint
which triggered the highlight.

Closes #8277.

Avoid collisions with IMEs by using ctrl+shift+o. ctrl+shift+u is bound
to open unicode input in a lot of IMEs by default meaning that users
won't ever see the url hints UI.

This patch allows running `alacritty migrate` to automatically apply
configuration changes made to the TOML format, like moving `ipc_socket`
to `general.ipc_socket`.

This should reduce the friction of moving around individual options
significantly, while also persisting the format of the existing TOML
file thanks to `toml_edit`.

The YAML migration has been simplified significantly to only switch the
format of the file from YAML to TOML. The new TOML features are used for
everything else.

Some users struggle with TOML, since root options must always be at the
top of the file, since they're otherwise associated with the last table.

To avoid misunderstandings, all root-level fields have been removed. A
new `general` section was added to allow housing configuration options
that do not fit into any more specific groups.

Closes #7906.

This patch checks the hash of the import paths on every config change
and restarts the config monitor whenever the current monitor's hash
diverges from the updated config's list of imports.

Closes #7981.

Co-authored-by: Christian Duerr <contact@christianduerr.com>