Add new multithreaded concurrency configuration

[qkoziol]

Added infrastructure support for multithreaded concurrency by adding an optional way to switch to using a non-recursive R/W lock for the global API lock. This is enabled with a new 'concurrency' configuration flag for the autotools & CMake builds, which is disabled by default.

When the 'concurrency' build option is chosen, the global API lock will use the R/W lock and all API calls currently will acquire a write lock, ensuring exclusive access by one thread. Over time, the API routines that are converted to support multithreaded concurrency will switch to acquiring a read lock instead.

Reentering the library from application callbacks is managed by the 'disable locking for this thread' (DLFTT) threadsafety protocol. This is internally handled within the H5_API_LOCK / H5_API_UNLOCK macros in H5private.h (as before), which invoke the 'dlftt' routines in H5TSint.c.

To support this change, the threadsafety configuration macros for the library have been updated:
- --enable-threadsafe now defines the H5_HAVE_THREADSAFE macro
- --enable-concurrency defines the H5_HAVE_CONCURRENCY macro
The new H5_HAVE_THREADSAFE_API macro is set if either H5_HAVE_THREADSAFE or H5_HAVE_CONCURRENCY is enabled.

New Github actions are added to include the concurrency configuration in the CI for the develop branch.

To support the new non-recursive R/W locking for API routines, some other changes are necessary:

• Added macro wrappers around all callback invocations that could call an
  application function, and therefore re-enter the library:
  H5_BEFORE_USER_CB* / H5_AFTER_USER_CB*

• Added H5_user_cb_prepare / H5_user_cb_restore routines that save the
  state of the library when callback leaves the library. Includes error
  stack and threadsafe reentry state currently.

There's also some small cleanups to various places in the library:

• Moved the H5E_mpi_error_str / H5E_mpi_error_str_len globals to be local for
  pushing MPI errors, so that multiple threads can't interfere with each
  other.

• Added H5TS_rwlock_trywrlock() routine to R/W lock interface.

• Emulate R/W locks on MacOS because its implementation of
  pthread_rwlock_wrlock() does not conform to the POSIX standard.

• Don't acquire the global API lock in H5close, since it's acquired in H5_term_library, which is necessary because H5_term_library is invoked via other code paths that don't hold the global API lock.

• Don't call H5Eget_auto2 API routine within H5_term_library.

• Switched 'return NULL' in H5allocate_memory to HGOTO_DONE(NULL).

• Switched H5Pget_file_space_strategy / H5Pset_file_space_strategy to use
  internal routines instead of API routines.

• Switched H5Oopen_by_addr & H5Ovisit1 to use internal routines instead of
  API routines.

• Fixed a few places in src/H5Odeprec.c where a major
  error ID was passed as a minor ID.

[qkoziol]

@derobins @fortnern @jhendersonHDF @mattjala - Can I get some reviews on this, I've got a sequence of branches queued after this one.

[mattjala]

Looks good besides a few missing blocks

[qkoziol]

Looks good besides a few missing blocks

Thanks for the review. There's no need for additional blocks, but I'll take out the definition for H5TS_init().