Use BytesView instead of Bytes (+add Utf8 hint type)

[applejag]

Changes to use BytesView more, as it seems to be a better convention for function parameters as Bytes implicitly converts to a BytesView.

I also added "hint alias types" for Utf8 and Utf8View to try better hint where UTF-8 input is required. Sadly the LSP currently only view the aliased type Bytes/BytesView, and doesn't even allow "jump to definition" for type aliases. And there's currently no way to get string literals to implicitly convert to custom types. Bummer. But maybe that will be fixed in the future?

One issue here is that using views will force import the stdlib's abort implementation, which does some string and SourceLoc shenaginans which brings in ~5kB of code: https://github.com/moonbitlang/core/blob/05aaf6a8164093e22247519255cccdcabd7870c6/builtin/intrinsics.mbt#L64-L78

No additional code is imported if the app already uses any other standard library function that calls @builtin.abort, which for more complicated projects is somewhat unavoidable.

[orsinium]

And there's currently no way to get string literals to implicitly convert to custom types.

Not good :( At least if I get it right. Most of the strings are static strings. Also, returning (for instance, from get_name) Bytes is better than BytesView since Bytes is more specific. "Be conservative in what you return".

[applejag]

To be clear, I meant "no way to get string literals on custom structs"

You do get the implicit conversion on type aliases, like we have in this PR.

However in this snippet:

firefly-moon/example/random/main.mbt

Lines 12 to 17 in 700fc8a

	@firefly.log_debug(("random float: " : Utf8) + format(@random.float()))
	@firefly.log_debug(("random double: " : Utf8) + format(@random.double()))
	@firefly.log_debug(("random int: " : Utf8) + format(@random.int()))
	@firefly.log_debug(("random uint: " : Utf8) + format(@random.uint()))
	@firefly.log_debug(("random int64: " : Utf8) + format(@random.int64()))
	@firefly.log_debug(("random uint64: " : Utf8) + format(@random.uint64()))

^I had to add the ( ... : Utf8) because when the parameter is a BytesView then the string literal was interpreted as a string when doing +

[orsinium]

Alright, I trust you. You're the MoonBit expert here :)