Upgrade 0 A.D. to Spidermonkey ESR 91

[wraitii]

Firefox 91, the next ESR, is planned to come out in July.

Setting up this ticket to log stuff in advance.

Potentially interesting: ​https://hg.mozilla.org/mozilla-central/rev/7c1dcab226105b4d4dab172021483381689dd6d7 (I had trouble with that and ultimately reverted to non-incremental GC)

Expect performance improvements this time around (see work on new Baseline interpreter)

[Arfrever Frehtes Taifersar Arahesis]

Commits related to Mozilla bug 1681268 were backported to ESR 78 branch:

​https://hg.mozilla.org/releases/mozilla-esr78/rev/9fad778aa3291ef630338bc568453a79faa37089

​https://hg.mozilla.org/releases/mozilla-esr78/rev/488097780e542ac1379b35c473ac5c06892810e1

And are included in SpiderMonkey 78.7.0 release.

Please firstly update SpiderMonkey used by 0 A.D. from 78.6.0 to 78.7.0.

[Freagarach]

Not happening before the release.

[wraitii]

In 26205:

Remove JS_New in favour of JS::Construct in preparation for SM91

Spidermonkey 91, the next ESR, removes JS_New in favour or JS::Construct.
See
​https://github.com/mozilla-spidermonkey/spidermonkey-embedding-examples/blob/migration-guide/docs/Migration%20Guide.md#object-construction
and
​https://bugzilla.mozilla.org/show_bug.cgi?id=1491055

This change is SM78 compatible and therefore done beforehand.

Tested by: Freagarach

Refs #5986

Differential Revision: ​https://code.wildfiregames.com/D4427

[Stan]

Unlikely to get done for A26

[jprahman]

ESR102 is out, may be worth looking into upgrading to ESR102 instead of ESR91 for the additional improvements in 102

[Freagarach]

Pushing back.

[Stan]

In 27409:

[SM91] Update to Spidermonkey 91.1.3 APIs
Fixes: #5986
Patch by: @wraitii
Comments by: @nwtour, @Stan

Differential Revision: ​https://code.wildfiregames.com/D4428