ci: GitHub Actions for arm64

ci: stop using deprecated set-env in GitHub Actions

(And move the ci scripts into the `ci` directory.)

Deprecate `is_valid_name` functions; replace with `name_is_valid` functions

Signed-off-by: Sven Strickroth <email@cs-ware.de>

Signed-off-by: Sven Strickroth <email@cs-ware.de>

Provide a function that can check remote name validity but can also
signal when an error occurs.  Use the name "name_is_valid", which is
more suggestive of checking a given name, rather than "is_valid_name",
which suggests that the function checks the validity of the current
remote's name.

Disambiguate invalid specifications in `git_refspec__parse` so that
callers can determine the difference between invalid specifications and
actual errors.  No call sites wil propagagte this new error message to
an end-user, so there is no user-facing API change.

Provide a function that can check reference name validity but can also
signal when an error occurs.  Use the name "name_is_valid", which is
more suggestive of checking a given name, rather than "is_valid_name",
which suggests that the function checks the validity of the current
reference's name.

Move `git_reference__is_valid_name` to `git_reference__name_is_valid`,
which returns errors and sets an out boolean parameter.

Include `${MBEDTLS_INCLUDE_DIR}` when compiling `crypt_mbedtls.c`

Without this, mbedTLS installs in non-default install locations
that are otherwise found by the `FindmbedTLS.cmake` module are not
found by the C preprocessor at compile time.

threadstate: rename tlsdata when building w/o threads

Refactor "global" state

Make the Windows leak detection more robust

Define `git___load` when building with `-DTHREADSAFE=OFF`

ntlm: update ntlm dependency for htonll

This should allow folks that build in non-thread-safe environments to
still be able to build the library.

Fixes: #5663

libgit2 v1.1.0

This change:

* Increases MY_ROW_LIMIT to 2M, since it has been failing in #5595's
  tests since it's _super_ close to the limit.
* Calls `git_repository_free()` on a `git_repository` that was being
  leaked only in Windows.
* Marks the global `git_repository` on `tests/repo/init.c` as `NULL`
  after being freed to make any accidental access more noisy.
* Uses `cl_assert_equal_i()` in `test_trace_windows_stacktrace__leaks`
  to make the test failures more actionable.
* Renames the globals in `tests/repo/init.c` so that they don't start
  with an underscore.

Now that we've identified that our global settings really aren't global
at all, and refactored the library to match that, change global.c to
libgit2.c, which is especially nice since the prefix of the functions
matches the filename.

Provide a mechanism for system components to register for initialization
and shutdown of the libgit2 runtime.

We want to store a pointer to emulate `pthread_exit` on Windows.  Do
this within the threading infrastructure so that it could potentially be
re-used outside of the context of libgit2 itself.

We were never properly testing git_thread_exit.  Do so.

Our "global initialization" has accumulated some debris over the years.
It was previously responsible for both running the various global
initializers (that set up various subsystems) _and_ setting up the
"global state", which is actually the thread-local state for things
like error reporting.

Separate the thread local state out into "threadstate".  Use the normal
subsystem initialization functions that we already have to set it up.
This makes both the global initialization system and the threadstate
system simpler to reason about.

Ensure that we can allocate the error message buffer.  In keeping with
our typical policiess, we allow (small) memory leaks in the case where
we're out of memory.

Move the mwindow mutex into the mwindow code itself, initializing it in
the mwindow global initialization function instead of in the global
initializer.