terminal: Add Alt+. keybinding passthrough for last-argument recall (#29088)

Alt+. is a useful terminal/readline feature that cycles through the last
arguments of previous commands in history. Unlike many other shortcuts,
it doesn't conflict with anything important globally, so it can be
safely enabled by default.

Release Notes:

- N/A

assets/keymaps/default-linux.json

@@ -920,6 +920,7 @@
       "ctrl-enter": "assistant::InlineAssist",
       "alt-b": ["terminal::SendText", "\u001bb"],
       "alt-f": ["terminal::SendText", "\u001bf"],
+      "alt-.": ["terminal::SendText", "\u001b."],
       // Overrides for conflicting keybindings
       "ctrl-b": ["terminal::SendKeystroke", "ctrl-b"],
       "ctrl-c": ["terminal::SendKeystroke", "ctrl-c"],

assets/keymaps/default-macos.json

@@ -1005,6 +1005,7 @@
       "alt-right": ["terminal::SendText", "\u001bf"],
       "alt-b": ["terminal::SendText", "\u001bb"],
       "alt-f": ["terminal::SendText", "\u001bf"],
+      "alt-.": ["terminal::SendText", "\u001b."],
       // There are conflicting bindings for these keys in the global context.
       // these bindings override them, remove at your own risk:
       "up": ["terminal::SendKeystroke", "up"],