Add --enable-asan and --enable-ubsan switches

`configure` now accepts `--enable-asan` and `--enable-ubsan` switches
which results in passing `-fsanitize=address`
and `-fsanitize=undefined`, respectively, to the compiler. Those
flags are enabled in GitHub workflows for ZTS and zloop. Errors
reported by both instrumentations are corrected, except for:

- Memory leak reporting is (temporarily) suppressed. The cost of
  fixing them is relatively high compared to the gains.

- Checksum computing functions in `module/zcommon/zfs_fletcher*`
  have UBSan errors suppressed. It is completely impractical
  to enforce 64-byte payload alignment there due to performance
  impact.

- There's no ASan heap poisoning in `module/zstd/lib/zstd.c`. A custom
  memory allocator is used there rendering that measure
  unfeasible.

- Memory leaks detection has to be suppressed for `cmd/zvol_id`.
  `zvol_id` is run by udev with the help of `ptrace(2)`. Tracing is
  incompatible with memory leaks detection.

Reviewed-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: szubersk <szuberskidamian@gmail.com>
Closes #12928

module/zcommon/zfs_fletcher.c

@@ -300,18 +300,21 @@ fletcher_2_byteswap(const void *buf, uint64_t size,
 	(void) fletcher_2_incremental_byteswap((void *) buf, size, zcp);
 }
 
+ZFS_NO_SANITIZE_UNDEFINED
 static void
 fletcher_4_scalar_init(fletcher_4_ctx_t *ctx)
 {
 	ZIO_SET_CHECKSUM(&ctx->scalar, 0, 0, 0, 0);
 }
 
+ZFS_NO_SANITIZE_UNDEFINED
 static void
 fletcher_4_scalar_fini(fletcher_4_ctx_t *ctx, zio_cksum_t *zcp)
 {
 	memcpy(zcp, &ctx->scalar, sizeof (zio_cksum_t));
 }
 
+ZFS_NO_SANITIZE_UNDEFINED
 static void
 fletcher_4_scalar_native(fletcher_4_ctx_t *ctx, const void *buf,
     uint64_t size)
@@ -335,6 +338,7 @@ fletcher_4_scalar_native(fletcher_4_ctx_t *ctx, const void *buf,
 	ZIO_SET_CHECKSUM(&ctx->scalar, a, b, c, d);
 }
 
+ZFS_NO_SANITIZE_UNDEFINED
 static void
 fletcher_4_scalar_byteswap(fletcher_4_ctx_t *ctx, const void *buf,
     uint64_t size)