This fixes a regression, likely introduced in 5d173f6df, which changed
the severity of missing imports from `info` back to `error`.

The cause of this issue was a more complicated error handling mechanism,
which explicitly translated IO errors to a separate enum variant without
accounting for it in all scenarios.

While retrospectively this seems completely unnecessary to me, it did
mean shorter error messages in case the main config file was not found.
To preserve the benefits of both approaches, explicit handling for the
`NotFound` IO error has been added when loading the main configuration
file.

This implements a coordinated shutdown of the config monitor by sending
an event to its thread and waiting for the thread to terminate.

Closes #7778.

This fixes an issue where the `Select` action for hyperlink escape text
would select the entire line, instead of selecting only the hyperlink
itself.

It also changes the way hyperlinks with the same ID are highlighted,
removing the restriction of being on consecutive lines and instead
highlighting all visible cells that correspond to the matching
hyperlink.

Closes #7766.

Fixes #7665.

Originally kitty defined that functional keys, which are not encoded
by default, like `Pause` should be encoded with `CSI u`. However
the specification was clarified and now it says that terminal
may ignore that part. Given that Alacritty tries to follow xterm/urxvt
when it comes to bindings, CSI u bindings are not send for consistency
reasons.

This also brings back F13-F20 bindings used by Alacritty in 0.12.3, as
well as explicitly defines `NumpadEnter` like it was before.

Closes #7623.

Closes #7592.