Don't relocate Apple Silicon bottles for default prefix

[MikeMcQuaid]

Verification

• This issue's title and/or description do not reference a single formula e.g. brew install wget. If they do, open an issue at https://github.com/Homebrew/homebrew-core/issues/new/choose instead.

Provide a detailed description of the proposed feature

We should avoid using e.g. @@HOMEBREW_PREFIX@@ etc. relocation replacements on Apple Silicon (and maybe Linux x86_64/arm64 but not/never macOS Intel).

These were needed initially because replacing /usr/local on macOS Intel was far too wide-reaching with too many false positives and negatives.

What is the motivation for the feature?

This would:

• simplify and speed up pouring on our widest used platform(s)
• potentially enable codesigning of homebrew-core packages for Apple Silicon (where we require cask code-signing anyway)
  • code-signing is broken by relocation

How will the feature be relevant to at least 90% of Homebrew users?

Increased speed and security for homebrew-core.

What alternatives to the feature have been considered?

• Doing nothing
• Having another tap that signs already-relocated bottles