Translate _d_arrayassign{,_l,_r} to templates

[teodutu]

• Implement template _d_arrayassign{_l,_r}.
• Lower array assignment expressions to the above templates.
• Remove old lowering from e2ir.d.
• Remove the old _d_arrayassign_{l,r} and _d_arrayassig as its usage was merged with _d_arrayassign_l.

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Testing this PR locally

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dub run digger -- build "master + dmd#14310"

[thewilsonator]

Could you please double check that the build kite failures are unrelated? Otherwise this looks good. Please ping me when you're done.

[teodutu]

@thewilsonator The buildkite failures were related. They were caused by the temporary variable used for _d_arrayappend_r:

_tmp = rhs, _d_arrayappend_r(lhs, _tmp);

I was not adding the maybescope storage class to _tmp so the compiler believed a scope rhs was ecaping. This caused both buildkite failures. They should work fine now.

[RazvanN7]

LGTM!

[RazvanN7]

cc @dkorpel

[schveiguy]

This change introduced unnecessary out-of-bounds checking when doing array operations. e.g.: https://github.com/dlang/dmd/pull/14310/files#diff-c9a721f453e1e17d997f8603ca3e4e65c765f0ebf0dd1cfb972ddddc959bdbb1R92-R94

[teodutu]

@schveiguy Are these checks relevant given that they're disabled when compiling with maximum optimisations, i.e. -O -release -inline -boundscheck=off?

[schveiguy]

Yes, they are relevant. First, because they are redundant, the entire operation is bounds checked first (see here)

And second, because it's a template, it will be compiled under whatever options the user is using at the time.

[CyberShadow]

This pull request introduced a regression:
https://issues.dlang.org/show_bug.cgi?id=23959