[mojo] Update the codebase to Mojo v0.26.1

[forfudan]

This pull request refactors the codebase to Mojo v0.26.1. The following changes are made.

• Replaces all alias declarations with comptime in all files. alias is deprecated.
• Updates list and constant construction syntax throughout the codebase, e.g., replaced List[UInt32](...) with [UInt32(...), ...], used [word] instead of List[UInt32](word). The old syntax is deprecated.
• Updates list slicing syntax to use the new syntax. Now lst[1:] returns a Span instead of a List, so it needs to be converted to a list using the constructor List(...).
• Updates some methods of the String type and the indexing and slicing syntax for String objects to match the latest Mojo syntax. The old syntax is deprecated.
• Fixes the closure capture when using vectorize. The new syntax requires something like unified {read x, mut y} to capture variables x and y in the closure. The old syntax is deprecated.