martinvuyk

Add string benchmarking infrastructure and basic benchmarks. Added data for benchmarking collections UN charter: Taken from the official [UN website](https://www.un.org/en/about-us/un-charter/full-text) with the language abbreviations following ISO 639-1 except simplified mandarin...

Optimize `_StringSliceIter` to not have branching in forward iteration Depends on: - PR #3529 for `fn _count_utf8_continuation_bytes()` - PR #3528 for `fn _utf8_first_byte_sequence_length()`

Add `String`, `StringSlice`, `Span`, and `List` method 'unsafe_slice()' Proposed solution for [this comment/issue](https://github.com/modularml/mojo/pull/3528#discussion_r1771784689) and for other performance sensitive use cases where the user would have to use `unsafe_ptr()` and repeat...

### Bug description Fix `String.find()` family of functions to work by unicode codepoints Indirectly related to comment/issue [#3246](https://github.com/modularml/mojo/issues/3246#issuecomment-2246123195) ### Steps to reproduce ... ### System information ```shell ... ```

[stdlib] Add `Optional` unwrap using `__getitem__ `

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Add `Optional` unwrap using `__getitem__ `