[InstrProf] Add the skipprofile attribute

As discussed in [0], this diff adds the `skipprofile` attribute to
prevent the function from being profiled while allowing profiled
functions to be inlined into it. The `noprofile` attribute remains
unchanged.

The `noprofile` attribute is used for functions where it is
dangerous to add instrumentation to while the `skipprofile` attribute is
used to reduce code size or performance overhead.

[0] https://discourse.llvm.org/t/why-does-the-noprofile-attribute-restrict-inlining/64108

Reviewed By: phosek

Differential Revision: https://reviews.llvm.org/D130807

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -1919,6 +1919,8 @@ static Attribute::AttrKind getAttrFromCode(uint64_t Code) {
     return Attribute::NoCfCheck;
   case bitc::ATTR_KIND_NO_PROFILE:
     return Attribute::NoProfile;
+  case bitc::ATTR_KIND_SKIP_PROFILE:
+    return Attribute::SkipProfile;
   case bitc::ATTR_KIND_NO_UNWIND:
     return Attribute::NoUnwind;
   case bitc::ATTR_KIND_NO_SANITIZE_BOUNDS: