[NFC] Change more startswith/endswith to starts_with/ends_with.

My previous PR to change startswith/endswith to starts_with/ends_with
was intended to be limited to C++ sources, as we have a number of
occurrences in Python files that should be left alone, but I did so by
limiting to *.cpp files, when actually we have a few in *.h files that
should be updated too.

Author: hvdijk

modules/compiler/spirv-ll/include/spirv-ll/builder.h

@@ -591,7 +591,7 @@ class Builder {
     llvm::SmallVector<llvm::StringRef, 16> subs;
     for (size_t nameIndex = 0; nameIndex < names.size(); nameIndex++) {
       llvm::StringRef name(names[nameIndex]);
-      if (name.startswith("Dv")) {
+      if (name.starts_with("Dv")) {
         auto found = std::find(subs.begin(), subs.end(), name);
         if (found == subs.end()) {
           subs.push_back(name);

modules/compiler/utils/include/compiler/utils/pipeline_parse_helpers.h

@@ -75,7 +75,7 @@ static bool checkParametrizedPassName(StringRef Name, StringRef PassName) {
   if (!Name.consume_front(PassName)) return false;
   // normal pass name w/o parameters == default parameters
   if (Name.empty()) return true;
-  return Name.startswith("<") && Name.endswith(">");
+  return Name.starts_with("<") && Name.ends_with(">");
 }
 
 inline Expected<StringRef> parseSinglePassStringRef(StringRef Params) {