[red-knot] Port type inference tests to new test framework (#13719)

## Summary

Porting infer tests to new markdown tests framework.

Link to the corresponding issue: #13696

---------

Co-authored-by: Carl Meyer <carl@astral.sh>

crates/red_knot_python_semantic/resources/mdtest/subscript/tuple.md

@@ -0,0 +1,21 @@
+# Tuple subscripts
+
+## Basic
+
+```py
+t = (1, 'a', 'b')
+
+a = t[0]
+b = t[1]
+c = t[-1]
+d = t[-2]
+e = t[4]        # error: [index-out-of-bounds]
+f = t[-4]       # error: [index-out-of-bounds]
+
+reveal_type(a)  # revealed: Literal[1]
+reveal_type(b)  # revealed: Literal["a"]
+reveal_type(c)  # revealed: Literal["b"]
+reveal_type(d)  # revealed: Literal["a"]
+reveal_type(e)  # revealed: Unknown
+reveal_type(f)  # revealed: Unknown
+```