Add --no-debug <regex> flag

[varphone]

This patch based on [Close #961] Add --no-debug flag #1190, thanks ivanovaleksey

Add --no-debug <regex> and Builder::no_debug(String) to supply regexes for matching against types that we should not derive or implement Debug for.

Adding this feature involves:

• Adding a new RegexSet member to bindgen::Builder (similar to the whitelisted_types set).
• A Builder method to add strings to that RegexSet.
• Plumbing in src/options.rs to convert --no-debug <regex> CLI flags into invocations of the builder method.
• Making the MonotoneFramework::constrain function in src/ir/analysis/derive_debug.rs check if the given item is explicitly marked not to be Debug, and if so, inserting it into the self.cannot_derive_debug set via return self.insert(id).
• Skipping any item explicitly marked not to be Debug in src/codegen/derive_debug.rs so that we don't generate an impl Debug for ... for these types when --impl-debug is passed.
• Tests!
  • When --impl-debug is also supplied
  • When --impl-debug is not also supplied
  • When the no-debug type is transitively referenced by a whitelisted item
  • When the no-debug type is explicitly whitelisted
  • When the no-debug type is marked opaque

[highfive]

Warning

• These commits modify unsafe code. Please review it carefully!

[emilio]

This looks great, thanks!

Mind fixing the struct name in the test? We can merge this with that.

[emilio]

This name seems copy-pasted, but inaccurate for this test, mind fixing it?

[emilio]

I did that tweak and merged. Thanks!