[ESIMD] Fix namespace and bug in the docs.

[kbobrovs]

No description provided.

[v-klochkov]

The changes are good.
IMO, there are few more places where changes are needed, e.g. the line 107:
sycl::ext::intel::experimental::esimd::block_store
-->
sycl::ext::intel::esimd::block_store

[kbobrovs]

Failures are unrelated:
Linking CXX shared library lib/libpi_level_zero.so
FAILED: lib/libpi_level_zero.so
...
pi_level_zero.cpp:(.text.piextProgramGetNativeHandle+0x54): undefined reference to `pthread_rwlock_rdlock

Since this patch touches only docs and doxygen task is OK, I'm merging.

[kbobrovs]

@smaslov-intel, please be aware of the libpi_level_zero.so build failure

[smaslov-intel]

@smaslov-intel, please be aware of the libpi_level_zero.so build failure

Thanks. This is already fixed in #6059

[kbobrovs]

The changes are good. IMO, there are few more places where changes are needed, e.g. the line 107: sycl::ext::intel::experimental::esimd::block_store --> sycl::ext::intel::esimd::block_store

Did not notice this message. You are right, will fix too.