Add more complete MSL passthrough

[SupaMaggie70Incorporated]

Connections
Related to #8139

Description
Previously, the load_shader function on metal backend would panic with panic!("load_shader required a naga shader"); if you tried to create a non-compute pipeline with a passthrough shader. This is a quick fix to address that

Testing
Already exists

Squash or Rebase?

Only commit is named "only commit hopefully" so probably squash

Checklist

• Run cargo fmt.
• Run taplo format.
• Run cargo clippy --tests. If applicable, add:
  • --target wasm32-unknown-unknown
• Run cargo xtask test to run tests.
• If this contains user-facing changes, add a CHANGELOG.md entry.

[cwfitzgerald]

Would be nice to get some tests in for this eventually.

[SupaMaggie70Incorporated]

Would be nice to get some tests in for this eventually.

Probably covered by #8128

[jimblandy]

@SupaMaggie70Incorporated @cwfitzgerald The commit message on 24a31c4 ("Only commit hopefully") is really not helpful. It's good that it links to the PR, but if we're going to try to help other developers, we need to give them just a brief summary of what the change is about.

[cwfitzgerald]

@jimblandy oh that's weird, I expected it to have the squashed commit name be the PR title, which is why I wasn't worried about. This is the first PR I merged on my phone in a while, I wonder if the mobile app does something weird....

[SupaMaggie70Incorporated]

@SupaMaggie70Incorporated @cwfitzgerald The commit message on 24a31c4 ("Only commit hopefully") is really not helpful. It's good that it links to the PR, but if we're going to try to help other developers, we need to give them just a brief summary of what the change is about.

The PR says this

Only commit is named "only commit hopefully" so probably squash

In the future I'll try to actually assign meaningful names to commits though

[jimblandy]

Okay, I see. Yes, even just the PR summary would be better. We now have two commits in the recent history with this same message.

[SupaMaggie70Incorporated]

Okay, I see. Yes, even just the PR summary would be better. We now have two commits in the recent history with this same message.

The previous commit having that name is why I added this to the summary XD