Reset the queue state between each command buffer on queue submit

[jleibs]

This is a port of #3589 to master

The move of reset_state from outside to inside the loop matches the previous behavior here: https://github.com/gfx-rs/gfx/blob/master/src/backend/gl/src/queue.rs#L1142

Given the command encoder assumes a default state this seems to be the only safe behavior to avoiding leaking state between buffers.

Additionally reset the state of SAMPLE_ALPHA_TO_COVERAGE as part of a queue reset.

Checklist

• Run cargo clippy.
• Run RUSTFLAGS=--cfg=web_sys_unstable_apis cargo clippy --target wasm32-unknown-unknown if applicable.
• Add change to CHANGELOG.md. See simple instructions inside file.

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Description
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Testing
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