languages: Fix Bash indentation issues with multi-cursors, newlines, and keyword outdenting (#35116)

Closes #34390

This PR fixes several Bash indentation issues:

- Adding indentation or comment using multi cursors no longer breaks
relative indentation
- Adding newline now places the cursor at the correct indent
- Typing a valid keyword triggers context-aware auto outdent

It also adds tests for all of them.

Release Notes:

- Fixed various issues with handling indentation in Bash.

crates/languages/src/bash/indents.scm

@@ -1,12 +1,12 @@
-(function_definition
-    "function"?
-    body: (
-        _
-        "{" @start
-        "}" @end
-    )) @indent
+(_ "[" "]" @end) @indent
+(_ "{" "}" @end) @indent
+(_ "(" ")" @end) @indent
 
-(array
-    "(" @start
-    ")" @end
-    ) @indent
+(function_definition) @start.function
+(if_statement) @start.if
+(elif_clause) @start.elif
+(else_clause) @start.else
+(for_statement) @start.for
+(while_statement) @start.while
+(case_statement) @start.case
+(case_item) @start.case_item