Support WebIDL `record<>`

[saschanaz]

Rebased @taki-zaro's work (#20318).

---

• ./mach build -d does not report any errors
• ./mach test-tidy does not report any errors
• These changes fix #15012 and closes #20318. Possibly also closes #21463.

• There are tests for these changes

---

This change is 

[highfive]

Heads up! This PR modifies the following files:

• @asajeffrey: components/script/dom/bindings/codegen/CodegenRust.py, components/script/dom/testbinding.rs, components/script/dom/bindings/mod.rs, components/script/dom/bindings/mozmap.rs, components/script/dom/bindings/record.rs and 2 more
• @KiChjang: components/script/dom/bindings/codegen/CodegenRust.py, components/script/dom/testbinding.rs, components/script/dom/bindings/mod.rs, components/script/dom/bindings/mozmap.rs, components/script/dom/bindings/record.rs and 2 more

[highfive]

Warning

• These commits modify unsafe code. Please review it carefully!

[saschanaz]

@bors-servo try=wpt

[bors-servo]

⌛ Trying commit 32913ef with merge ec4ae48...

[bors-servo]

💔 Test failed - linux-rel-wpt

[CYBAI]

Cool! Looks like more PASS tests 👀

{
    "status": "PASS", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": "Basic operation with one property", 
    "test": "/fetch/api/headers/headers-record.html", 
    "line": 77071, 
    "action": "test_result", 
    "expected": "FAIL"
}
{
    "status": "PASS", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": "Basic operation with one property and a proto", 
    "test": "/fetch/api/headers/headers-record.html", 
    "line": 77072, 
    "action": "test_result", 
    "expected": "FAIL"
}
{
    "status": "PASS", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": "Correct operation ordering with two properties", 
    "test": "/fetch/api/headers/headers-record.html", 
    "line": 77073, 
    "action": "test_result", 
    "expected": "FAIL"
}
{
    "status": "PASS", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": "Correct operation ordering with two properties one of which has an invalid value", 
    "test": "/fetch/api/headers/headers-record.html", 
    "line": 77075, 
    "action": "test_result", 
    "expected": "FAIL"
}
{
    "status": "PASS", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": "Correct operation ordering with non-enumerable properties", 
    "test": "/fetch/api/headers/headers-record.html", 
    "line": 77076, 
    "action": "test_result", 
    "expected": "FAIL"
}
{
    "status": "PASS", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": "Correct operation ordering with undefined descriptors", 
    "test": "/fetch/api/headers/headers-record.html", 
    "line": 77077, 
    "action": "test_result", 
    "expected": "FAIL"
}
{
    "status": "PASS", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": "Operation with non-enumerable Symbol keys", 
    "test": "/fetch/api/headers/headers-record.html", 
    "line": 77080, 
    "action": "test_result", 
    "expected": "FAIL"
}
{
    "status": "PASS", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": "URLSearchParams constructor, DOMException as argument", 
    "test": "/url/urlsearchparams-constructor.any.worker.html", 
    "line": 136213, 
    "action": "test_result", 
    "expected": "FAIL"
}
{
    "status": "PASS", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": "URLSearchParams constructor, DOMException as argument", 
    "test": "/url/urlsearchparams-constructor.any.html", 
    "line": 229104, 
    "action": "test_result", 
    "expected": "FAIL"
}

[saschanaz]

@bors-servo try=wpt

Two Headers tests are still failing, need to investigate. DevTools connection fails on both stable and nightly Firefox, is it #24092?

[bors-servo]

⌛ Trying commit 935a084 with merge d71a49c...

[bors-servo]

☀️ Test successful - linux-rel-css, linux-rel-wpt, status-taskcluster
State: approved= try=True

[saschanaz]

@bors-servo try=wpt

[bors-servo]

⌛ Trying commit 6c96ad6 with merge b08fe84...

[bors-servo]

☀️ Test successful - linux-rel-css, linux-rel-wpt, status-taskcluster
State: approved= try=True

[nox]

Some changes and a couple of questions.

[saschanaz]

@bors-servo try=wpt

[bors-servo]

⌛ Trying commit 04489ed with merge a754f7e...

[bors-servo]

💔 Test failed - linux-rel-wpt

[saschanaz]

@bors-servo retry

[bors-servo]

⌛ Trying commit 04489ed with merge a4e3b90...

[saschanaz]

@nox, r?

[nox]

Please squash all the commits together so I can start reviewing one last time.

[saschanaz]

Everything in one commit?

Edit: Done, feel free to ping if this wasn't what you wanted as I got a backup.

[nox]

Looks good!

@bors-servo r+

[bors-servo]

📌 Commit b697621 has been approved by nox

[bors-servo]

⌛ Testing commit b697621 with merge dce8f93...

[bors-servo]

💔 Test failed - status-taskcluster

[saschanaz]

@bors-servo retry

[jdm]

@bors-servo retry
#23290

[bors-servo]

💣 Failed to start rebuilding: Unknown error

[bors-servo]

⌛ Testing commit b697621 with merge c5d6bb6...

[bors-servo]

☀️ Test successful - linux-rel-css, linux-rel-wpt, status-taskcluster
Approved by: nox
Pushing c5d6bb6 to master...