Draft: Resolve implicit-width-truncation warnings

[tynan-jdwk]

firtool-1.154.0 and later warn on all implicit width truncations (llvm/circt#10621). These width truncations were flagged in stock Chipyard builds.

This is marked as a draft PR while these PRs still need to be merged:

• Resolve implicit-width-truncation warnings testchipip#278
• Explicitly truncate wide-RHS assignments berkeley-hardfloat#93
• Resolve implicit-width-truncation warnings chipsalliance/rocket-chip-blocks#36
• Resolve implicit-width-truncation warnings chipsalliance/rocket-chip-inclusive-cache#45
• Resolve implicit-width-truncation warnings chipsalliance/rocket-chip#3822

Related PRs / Issues:

Type of change:

• Bug fix
• New feature
• Other enhancement

Impact:

• RTL change
• Software change (RISC-V software)
• Build system change
• Other

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• Did you set main as the base branch?
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• Did you delete any extraneous prints/debugging code?
• Did you mark the PR with a changelog: label?
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