Currently, we always pass the "selected" execution context to the
statusline. When handling a process or thread event, we can be more
precise, and build an execution context from the event data. This PR
also adopts the new `StoppedExecutionContext` that was recently
introduced.

The PR https://github.com/llvm/llvm-project/pull/152020 got merged by
accident. This commit addresses some follow up review comments.

Prior to this patch, SBFrame/SBThread methods exhibit racy behavior if
called while the process is running, because they do not lock the
`Process::RetRunLock` mutex. If they did, they would fail, correctly
identifying that the process is not running.

Some methods _attempt_ to protect against this with the pattern:

```
ExecutionContext exe_ctx(m_opaque_sp.get(), lock); // this is a different lock
Process *process = exe_ctx.GetProcessPtr();
if (process) {
  Process::StopLocker stop_locker;
  if (stop_locker.TryLock(&process->GetRunLock()))
        .... do work ...
```

However, this is also racy: the constructor of `ExecutionContext` will
access the frame list, which is something that can only be done once the
process is stopped.

With this patch:

1. The constructor of `ExecutionContext` now expects a `ProcessRunLock`
as an argument. It attempts to lock the run lock, and only fills in
information about frames and threads if the lock can be acquired.
Callers of the constructor are expected to check the lock.
2. All uses of ExecutionContext are adjusted to conform to the above.
3. The SBThread.cpp-defined helper function ResumeNewPlan now expects a
locked ProcessRunLock as _proof_ that the execution is stopped. It will
unlock the mutex prior to resuming the process.

This commit exposes many opportunities for early-returns, but these
would increase the diff of this patch and distract from the important
changes, so we opt not to do it here.

The ctor that takes a reference to ExecutionContextRef can be
implemented in terms of the ctor that takes a pointer to that object,
removing code duplication.

This is a user facing action, it is meant to focus the user's attention on
something other than the 0th frame when you stop somewhere where that's
helpful. For instance, stopping in pthread_kill after an assert will select
the assert frame.

This is not something you want to have happen internally in lldb, both
because internally you really don't want the selected frame changing out
from under you, and because the recognizers can do arbitrary work, and that
can cause deadlocks or other unexpected behavior.

However, it's not something that the current code does
explicitly after a stop has been delivered, it's expected to happen implicitly
as part of stopping. I changing this to call SMRF explicitly after a user
stop, but that got pretty ugly quickly.

So I added a bool to control whether to run this and audited all the current
uses to determine whether we're returning to the user or not.

Differential Revision: https://reviews.llvm.org/D148863

Applied modernize-use-equals-default clang-tidy check over LLDB.

This check is already present in the lldb/.clang-tidy config.

Differential Revision: https://reviews.llvm.org/D121844

Applied modernize-use-default-member-init clang-tidy check over LLDB.
It appears in many files we had already switched to in class member init but
never updated the constructors to reflect that. This check is already present in
the lldb/.clang-tidy config.

Differential Revision: https://reviews.llvm.org/D121481

This converts a default constructor's member initializers into C++11
default member initializers. This patch was automatically generated with
clang-tidy and the modernize-use-default-member-init check.

$ run-clang-tidy.py -header-filter='lldb' -checks='-*,modernize-use-default-member-init' -fix

This is a mass-refactoring patch and this commit will be added to
.git-blame-ignore-revs.

Differential revision: https://reviews.llvm.org/D103483

Summary:
A *.cpp file header in LLDB (and in LLDB) should like this:
```
//===-- TestUtilities.cpp -------------------------------------------------===//
```
However in LLDB most of our source files have arbitrary changes to this format and
these changes are spreading through LLDB as folks usually just use the existing
source files as templates for their new files (most notably the unnecessary
editor language indicator `-*- C++ -*-` is spreading and in every review
someone is pointing out that this is wrong, resulting in people pointing out that this
is done in the same way in other files).

This patch removes most of these inconsistencies including the editor language indicators,
all the different missing/additional '-' characters, files that center the file name, missing
trailing `===//` (mostly caused by clang-format breaking the line).

Reviewers: aprantl, espindola, jfb, shafik, JDevlieghere

Reviewed By: JDevlieghere

Subscribers: dexonsmith, wuzish, emaste, sdardis, nemanjai, kbarton, MaskRay, atanasyan, arphaman, jfb, abidh, jsji, JDevlieghere, usaxena95, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D73258

Currently ExecutionContext::GetByteOrder() always returns the host byte
order. This seems like a simple mistake: the return keyword appears to
have been omitted by accident. This patch fixes that and adds a unit
test.

Bugreport: https://llvm.org/PR37950

Differential revision: https://reviews.llvm.org/D48704

llvm-svn: 368181