Add Pyodide support (#12731)

This includes some initial work on adding Pyodide support (issue
#12729). It is enough to get
```
uv pip compile -p /path/to/pyodide --extra-index-url file:/path/to/simple-index
```
to work which should already be quite useful.

## Test Plan

* added a unit test for `pyodide_platform`
* integration tested manually with:
```
cargo run pip install \
-p /home/rchatham/Documents/programming/tmp/pyodide-venv-test/.pyodide-xbuildenv-0.29.3/0.27.4/xbuildenv/pyodide-root/dist/python \
--extra-index-url file:/home/rchatham/Documents/programming/tmp/pyodide-venv-test/.pyodide-xbuildenv-0.29.3/0.27.4/xbuildenv/pyodide-root/package_index \
--index-strategy unsafe-best-match --target blah --no-build \
numpy pydantic
```

---------

Co-authored-by: konsti <konstin@mailbox.org>
Co-authored-by: Zanie Blue <contact@zanie.dev>

docs/reference/cli.md

@@ -1702,6 +1702,7 @@ interpreter. Use <code>--universal</code> to display the tree for all platforms,
 <li><code>aarch64-manylinux_2_38</code>:  An ARM64 target for the <code>manylinux_2_38</code> platform</li>
 <li><code>aarch64-manylinux_2_39</code>:  An ARM64 target for the <code>manylinux_2_39</code> platform</li>
 <li><code>aarch64-manylinux_2_40</code>:  An ARM64 target for the <code>manylinux_2_40</code> platform</li>
+<li><code>wasm32-pyodide2024</code>:  A wasm32 target using the the Pyodide 2024 platform. Meant for use with Python 3.12</li>
 </ul></dd><dt id="uv-tree--python-version"><a href="#uv-tree--python-version"><code>--python-version</code></a> <i>python-version</i></dt><dd><p>The Python version to use when filtering the tree.</p>
 <p>For example, pass <code>--python-version 3.10</code> to display the dependencies that would be included when installing on Python 3.10.</p>
 <p>Defaults to the version of the discovered Python interpreter.</p>
@@ -3295,6 +3296,7 @@ by <code>--python-version</code>.</p>
 <li><code>aarch64-manylinux_2_38</code>:  An ARM64 target for the <code>manylinux_2_38</code> platform</li>
 <li><code>aarch64-manylinux_2_39</code>:  An ARM64 target for the <code>manylinux_2_39</code> platform</li>
 <li><code>aarch64-manylinux_2_40</code>:  An ARM64 target for the <code>manylinux_2_40</code> platform</li>
+<li><code>wasm32-pyodide2024</code>:  A wasm32 target using the the Pyodide 2024 platform. Meant for use with Python 3.12</li>
 </ul></dd><dt id="uv-pip-compile--python-version"><a href="#uv-pip-compile--python-version"><code>--python-version</code></a> <i>python-version</i></dt><dd><p>The Python version to use for resolution.</p>
 <p>For example, <code>3.8</code> or <code>3.8.17</code>.</p>
 <p>Defaults to the version of the Python interpreter used for resolution.</p>
@@ -3533,6 +3535,7 @@ be used with caution, as it can modify the system Python installation.</p>
 <li><code>aarch64-manylinux_2_38</code>:  An ARM64 target for the <code>manylinux_2_38</code> platform</li>
 <li><code>aarch64-manylinux_2_39</code>:  An ARM64 target for the <code>manylinux_2_39</code> platform</li>
 <li><code>aarch64-manylinux_2_40</code>:  An ARM64 target for the <code>manylinux_2_40</code> platform</li>
+<li><code>wasm32-pyodide2024</code>:  A wasm32 target using the the Pyodide 2024 platform. Meant for use with Python 3.12</li>
 </ul></dd><dt id="uv-pip-sync--python-version"><a href="#uv-pip-sync--python-version"><code>--python-version</code></a> <i>python-version</i></dt><dd><p>The minimum Python version that should be supported by the requirements (e.g., <code>3.7</code> or <code>3.7.9</code>).</p>
 <p>If a patch version is omitted, the minimum patch version is assumed. For example, <code>3.7</code> is mapped to <code>3.7.0</code>.</p>
 </dd><dt id="uv-pip-sync--quiet"><a href="#uv-pip-sync--quiet"><code>--quiet</code></a>, <code>-q</code></dt><dd><p>Use quiet output.</p>
@@ -3796,6 +3799,7 @@ should be used with caution, as it can modify the system Python installation.</p
 <li><code>aarch64-manylinux_2_38</code>:  An ARM64 target for the <code>manylinux_2_38</code> platform</li>
 <li><code>aarch64-manylinux_2_39</code>:  An ARM64 target for the <code>manylinux_2_39</code> platform</li>
 <li><code>aarch64-manylinux_2_40</code>:  An ARM64 target for the <code>manylinux_2_40</code> platform</li>
+<li><code>wasm32-pyodide2024</code>:  A wasm32 target using the the Pyodide 2024 platform. Meant for use with Python 3.12</li>
 </ul></dd><dt id="uv-pip-install--python-version"><a href="#uv-pip-install--python-version"><code>--python-version</code></a> <i>python-version</i></dt><dd><p>The minimum Python version that should be supported by the requirements (e.g., <code>3.7</code> or <code>3.7.9</code>).</p>
 <p>If a patch version is omitted, the minimum patch version is assumed. For example, <code>3.7</code> is mapped to <code>3.7.0</code>.</p>
 </dd><dt id="uv-pip-install--quiet"><a href="#uv-pip-install--quiet"><code>--quiet</code></a>, <code>-q</code></dt><dd><p>Use quiet output.</p>