Update tests to Unicode 16.0

[hsivonen]

This updates the tests to Unicode 16.0. The test harness needs changes, because the earlier test suite had a bug concerning trailing dots. Now the test suite matches the spec text, but the deprecated idna API retains the behavior that was written to the old test suite bug.

It is somewhat unfortunate the test suite is in this repo, but whether the code performs Unicode 16.0 behavior is up to the dependencies. Therefore, the expected landing sequence is this:

1. This PR (hopefully!) gets approved.
2. Publish idna_adapter 1.2.1 from its main branch.
3. Publish idna_mapping 1.1.0 from its main branch.
4. Land this PR.

[hsivonen]

And the tests here are, of course, failing, because the new versions of the dependencies haven't been published, yet.

Also, once idna_adapter 1.2.1 is published, the rust-url CI Rust version with default idna_adapter needs to be raised to 1.82.

[hsivonen]

And, of course ICU4X 1.x doesn't work with Unicode 16.0 test data, so that can't be tested.

[hsivonen]

And, indeed, there are enough changes that the old test suite does not pass with Unicode 16.0 implementation internals.

[hsivonen]

Timings building reqwest trunk on M3 Pro:

Back end	Debug	Release
ICU4X 2.0	6.0 s	7.7 s
ICU4X 1.5	6.2 s	8.1 s
unicode-rs	5.2 s	7.1 s
no-unicode	5.0 s	6.8 s

[hsivonen]

Updating from ICU4X 1.5 (Unicode 15.1) to 2.0 (Unicode 16.0) increases the Brotli-compressed wasm-opt-optimized wasm footprint of rust-url by 2273 bytes.

[hsivonen]

ICU4X 1.5:

test to_ascii_already_puny_label ... bench:         114 ns/iter (+/- 1)
test to_ascii_cow_hyphen         ... bench:          30 ns/iter (+/- 1)
test to_ascii_cow_leading_digit  ... bench:          57 ns/iter (+/- 0)
test to_ascii_cow_plain          ... bench:          11 ns/iter (+/- 0)
test to_ascii_cow_punycode_ltr   ... bench:         253 ns/iter (+/- 7)
test to_ascii_cow_punycode_mixed ... bench:         155 ns/iter (+/- 6)
test to_ascii_cow_punycode_rtl   ... bench:         242 ns/iter (+/- 4)
test to_ascii_cow_unicode_ltr    ... bench:         293 ns/iter (+/- 14)
test to_ascii_cow_unicode_mixed  ... bench:         208 ns/iter (+/- 9)
test to_ascii_cow_unicode_rtl    ... bench:         283 ns/iter (+/- 3)
test to_ascii_merged             ... bench:         227 ns/iter (+/- 4)
test to_ascii_puny_label         ... bench:         133 ns/iter (+/- 1)
test to_ascii_simple             ... bench:          28 ns/iter (+/- 1)
test to_unicode_ascii            ... bench:          26 ns/iter (+/- 0)
test to_unicode_merged_label     ... bench:         257 ns/iter (+/- 1)
test to_unicode_puny_label       ... bench:         120 ns/iter (+/- 1)

ICU4X 2.0:

test to_ascii_already_puny_label ... bench:         104 ns/iter (+/- 3)
test to_ascii_cow_hyphen         ... bench:          26 ns/iter (+/- 0)
test to_ascii_cow_leading_digit  ... bench:          52 ns/iter (+/- 1)
test to_ascii_cow_plain          ... bench:           8 ns/iter (+/- 0)
test to_ascii_cow_punycode_ltr   ... bench:         223 ns/iter (+/- 12)
test to_ascii_cow_punycode_mixed ... bench:         141 ns/iter (+/- 1)
test to_ascii_cow_punycode_rtl   ... bench:         225 ns/iter (+/- 13)
test to_ascii_cow_unicode_ltr    ... bench:         261 ns/iter (+/- 3)
test to_ascii_cow_unicode_mixed  ... bench:         197 ns/iter (+/- 4)
test to_ascii_cow_unicode_rtl    ... bench:         261 ns/iter (+/- 4)
test to_ascii_merged             ... bench:         199 ns/iter (+/- 4)
test to_ascii_puny_label         ... bench:         122 ns/iter (+/- 0)
test to_ascii_simple             ... bench:          23 ns/iter (+/- 0)
test to_unicode_ascii            ... bench:          22 ns/iter (+/- 0)
test to_unicode_merged_label     ... bench:         202 ns/iter (+/- 2)
test to_unicode_puny_label       ... bench:         112 ns/iter (+/- 1)

[codecov]

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@@           Coverage Diff           @@
##             main    #1045   +/-   ##
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  Coverage        ?   80.11%           
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  Files           ?       24           
  Lines           ?     4355           
  Branches        ?        0           
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  Hits            ?     3489           
  Misses          ?      866           
  Partials        ?        0           

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