Support inline fixers for fix and warn plugin

[orchestr7]

We need to support the following LIT fixers:
https://github.com/llvm/llvm-project/blob/main/clang-tools-extra/test/clang-tidy/checkers/abseil-time-comparison.cpp

// CHECK-MESSAGES: [[@LINE-1]]:7: warning: perform comparison in the time domain [abseil-time-comparison]
// CHECK-FIXES: absl::FromUnixSeconds(x) <= t1;

We need to:

1. Support this logic in a fix and warn plugin
2. To do this we need to generate tmp Expected test resource
3. Compare files and check results

This should be done under inlineFixer = true option

Keep in mind, that in warn plugin you already have the list with warnings matched to lines, may be it could help you

[orchestr7]

Bad news are the following:

1. I do not know how the following code works:

void g() {
  // CHECK-NOTES: [[@LINE+4]]:5: warning: argument name 'y' in comment does not match parameter name 'x'
  // CHECK-NOTES: [[@LINE-3]]:12: note: 'x' declared here
  // CHECK-NOTES: [[@LINE+2]]:14: warning: argument name 'z' in comment does not match parameter name 'y'
  // CHECK-NOTES: [[@LINE-5]]:19: note: 'y' declared here
  f(/*y=*/0, /*z=*/0);
  // CHECK-FIXES: {{^}}  f(/*y=*/0, /*z=*/0);

  f(/*x=*/1, /*y=*/1);

  ffff(0 /*aaaa=*/, /*bbbb*/ 0); // Unsupported formats.
}

2. And how the following multi-line fixes are working:

  int VeryVeryVeryVeryLongVariableName;
  absl::Time SomeTime;
  if (some_condition && very_very_very_very_long_variable_name
     < absl::ToUnixSeconds(SomeTime)) {
  // CHECK-MESSAGES: [[@LINE-2]]:25: warning: perform comparison in the time domain [abseil-time-comparison]
  // CHECK-FIXES: if (some_condition && absl::FromUnixSeconds(very_very_very_very_long_variable_name) < SomeTime) {
    return;
  }

[orchestr7]

The check_clang_tidy.py script provides an easy way to test both diagnostic messages and fix-its. It filters out CHECK lines from the test file, runs clang-tidy and verifies messages and fixes with two separate FileCheck invocations: once with FileCheck’s directive prefix set to CHECK-MESSAGES, validating the diagnostic messages, and once with the directive prefix set to CHECK-FIXES, running against the fixed code (i.e., the code after generated fix-its are applied). In particular, CHECK-FIXES: can be used to check that code was not modified by fix-its, by checking that it is present unchanged in the fixed code. The full set of FileCheck directives is available (e.g., CHECK-MESSAGES-SAME:, CHECK-MESSAGES-NOT:), though typically the basic CHECK forms (CHECK-MESSAGES and CHECK-FIXES) are sufficient for clang-tidy tests. Note that the FileCheck documentation mostly assumes the default prefix (CHECK), and hence describes the directive as CHECK:, CHECK-SAME:, CHECK-NOT:, etc. Replace CHECK by either CHECK-FIXES or CHECK-MESSAGES for clang-tidy tests.

[kgevorkyan]

@akuleshov7 btw, why it still pinned? I think we can drop it for now