Auto merge of #29921 - mrobinson:rename-wpt-tests-directory, r=atbrakhi

Rename `tests/wpt/web-platform-tests` to `tests/wpt/tests`

Rename the WPT tests directory to be more consistent with other WPT suites and
also to match what is done in Gecko. This makes things a bit simpler to type.

- Move tests/wpt/web-platform-tests to tests/wpt/tests
- Update scripts to reflect new WPT directory name

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---
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] There are tests for these changes OR

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tests/wpt/README.md

@@ -9,7 +9,7 @@ In particular, this folder contains:
 
 * `config.ini`: some configuration for the web-platform-tests.
 * `include.ini`: the subset of web-platform-tests we currently run.
-* `web-platform-tests`: copy of the web-platform-tests.
+* `tests`: copy of the web-platform-tests.
 * `meta`: expected failures for the web-platform-tests we run.
 * `mozilla`: web-platform-tests that cannot be upstreamed.
 
@@ -24,7 +24,7 @@ stdout.
 A subset of tests may be run by providing positional arguments to the
 mach command, either as filesystem paths or as test urls e.g.
 
-    ./mach test-wpt tests/wpt/web-platform-tests/dom/historical.html
+    ./mach test-wpt tests/wpt/tests/dom/historical.html
 
 to run the dom/historical.html test, or
 
@@ -59,8 +59,8 @@ can only run one WPT server at a time. To fix this:
 1. Follow the steps in [**Running the tests manually**](#running-the-tests-manually)
 2. Add a `break` to [start_servers in serve.py](https://github.com/servo/servo/blob/ce92b7bfbd5855aac18cb4f8a8ec59048041712e/tests/wpt/web-platform-tests/tools/serve/serve.py#L745-L783) as follows:
     ```
-    --- a/tests/wpt/web-platform-tests/tools/serve/serve.py
-    +++ b/tests/wpt/web-platform-tests/tools/serve/serve.py
+    --- a/tests/wpt/tests/tools/serve/serve.py
+    +++ b/tests/wpt/tests/tools/serve/serve.py
     @@ -746,6 +746,7 @@ def start_servers(logger, host, ports, paths, routes, bind_address, config,
                        mp_context, log_handlers, **kwargs):
          servers = defaultdict(list)

tests/wpt/config.ini

@@ -12,7 +12,7 @@ sync_path = sync
 run-info = .
 
 [manifest:upstream]
-tests = web-platform-tests
+tests = tests
 metadata = meta
 url-base = /