Fix all warnings given by UBSAN

The 'special' cases where we disable, suppress or circumvent UBSAN are:
- ref10 source (as here we intentionally do some shifts that UBSAN
  complains about.
- x86 version of optimized int#korr() methods. UBSAN do not like unaligned
  memory access of integers.  Fixed by using byte_order_generic.h when
  compiling with UBSAN
- We use smaller thread stack with ASAN and UBSAN, which forced me to
  disable a few tests that prints the thread stack size.
- Verifying class types does not work for shared libraries. I added
  suppression in mysql-test-run.pl for this case.
- Added '#ifdef WITH_UBSAN' when using integer arithmetic where it is
  safe to have overflows (two cases, in item_func.cc).

Things fixed:
- Don't left shift signed values
  (byte_order_generic.h, mysqltest.c, item_sum.cc and many more)
- Don't assign not non existing values to enum variables.
- Ensure that bool and enum values are properly initialized in
  constructors.  This was needed as UBSAN checks that these types has
  correct values when one copies an object.
  (gcalc_tools.h, ha_partition.cc, item_sum.cc, partition_element.h ...)
- Ensure we do not called handler functions on unallocated objects or
  deleted objects.
  (events.cc, sql_acl.cc).
- Fixed bugs in Item_sp::Item_sp() where we did not call constructor
  on Query_arena object.
- Fixed several cast of objects to an incompatible class!
  (Item.cc, Item_buff.cc, item_timefunc.cc, opt_subselect.cc, sql_acl.cc,
   sql_select.cc ...)
- Ensure we do not do integer arithmetic that causes over or underflows.
  This includes also ++ and -- of integers.
  (Item_func.cc, Item_strfunc.cc, item_timefunc.cc, sql_base.cc ...)
- Added JSON_VALUE_UNITIALIZED to json_value_types and ensure that
  value_type is initialized to this instead of to -1, which is not a valid
  enum value for json_value_types.
- Ensure we do not call memcpy() when second argument could be null.

Other things:

- Changed struct st_position to an OBJECT and added an initialization
  function to it to ensure that we do not copy or use uninitialized
  members. The change to a class was also motived that we used "struct
  st_position" and POSITION randomly trough the code which was
  confusing.
- Notably big rewrite in sql_acl.cc to avoid using deleted objects.
- Changed in sql_partition to use '^' instead of '-'. This is safe as
  the operator is either 0 or 0x8000000000000000ULL.
- Added check for select_nr < INT_MAX in JOIN::build_explain() to
  avoid bug when get_select() could return NULL.
- Reordered elements in POSITION for better alignment.
- Changed sql_test.cc::print_plan() to use pointers instead of objects.
- Fixed bug in find_set() where could could execute '1 << -1'.
- Added variable have_sanitizer, used by mtr.  (This variable was before
  only in 10.5 and up).  It can now have one of two values:
  ASAN or UBSAN.
- Moved ~Archive_share() from ha_archive.cc to ha_archive.h and marked
  it virtual. This was an effort to get UBSAN to work with loaded storage
  engines. I kept the change as the new place is better.
- Added in CONNECT engine COLBLK::SetName(), to get around a wrong cast
  in tabutil.cpp.

Changes that should not be needed but had to be done to suppress warnings
from UBSAN:

- Added static_cast<<uint16_t>> around shift to get rid of a LOT of
  compiler warnings when using UBSAN.
- Had to change some '/' of 2 base integers to shift to get rid of
  some compile time warnings.

Fixes:

MDEV-25505 Assertion `old_flags == ((my_flags & 0x10000U) ? 1 : 0)
fixed (was caused by an old version if this commit).

Reviewed by:
- Json changes: Alexey Botchkov
- Charset changes in ctype-uca.c: Alexander Barkov
- InnoDB changes: Marko Mäkelä
- sql_acl.cc changes: Vicențiu Ciorbaru
- build_explain() changes: Sergey Petrunia
Temporary commit to log changes for UBSAN

storage/mroonga/vendor/groonga/lib/io.c

@@ -337,7 +337,7 @@ grn_io_create(grn_ctx *ctx, const char *path, uint32_t header_size,
         if ((io = GRN_MALLOCN(grn_io, 1))) {
           grn_io_mapinfo *maps = NULL;
           if ((maps = GRN_CALLOC(sizeof(grn_io_mapinfo) * max_segment))) {
-            grn_strncpy(io->path, PATH_MAX, path, PATH_MAX);
+            grn_strncpy(io->path, PATH_MAX-1, path, PATH_MAX-1);
             io->header = header;
             io->user_header = (((byte *) header) + IO_HEADER_SIZE);
             io->maps = maps;
@@ -656,7 +656,7 @@ grn_io_open(grn_ctx *ctx, const char *path, grn_io_mode mode)
       if ((io = GRN_MALLOC(sizeof(grn_io)))) {
         grn_io_mapinfo *maps = NULL;
         if ((maps = GRN_CALLOC(sizeof(grn_io_mapinfo) * max_segment))) {
-          grn_strncpy(io->path, PATH_MAX, path, PATH_MAX);
+          grn_strncpy(io->path, PATH_MAX-1, path, PATH_MAX-1);
           io->header = header;
           io->user_header = (((byte *) header) + IO_HEADER_SIZE);
           {

storage/mroonga/vendor/groonga/lib/ts/ts_expr_node.c

@@ -1787,7 +1787,7 @@ grn_ts_expr_key_node_filter(grn_ctx *ctx, grn_ts_expr_key_node *node,
                             grn_ts_record *out, size_t *n_out)
 {
   size_t i, count;
-  grn_ts_bool key;
+  grn_ts_bool key= 0;
   switch (node->table->header.type) {
     case GRN_TABLE_HASH_KEY: {
       grn_hash *hash = (grn_hash *)node->table;
@@ -1831,7 +1831,7 @@ grn_ts_expr_key_node_adjust(grn_ctx *ctx, grn_ts_expr_key_node *node,
                             grn_ts_record *io, size_t n_io)
 {
   size_t i;
-  grn_ts_float key;
+  grn_ts_float key= 0;
   switch (node->table->header.type) {
     case GRN_TABLE_HASH_KEY: {
       grn_hash *hash = (grn_hash *)node->table;