samples/tests: bluetooth: Remove qemu_cortex_m3

Remove qemu_cortex_m3 from various bluetooth tests and samples since
they enable NVS which requires CONFIG_FLASH_PAGE_LAYOUT which is
not supported on qemu_cortex_m3 since there is no flash driver.

We get build failures with the arm-clang compiler because nvs.c
is referencing z_impl_flash_get_page_info_by_offs which does not
exist.

Switch to qemu_x86 as the integration_platforms if it was
qemu_cortex_m3 before.

Removed the bluetooth.mesh.mesh_shell.reduced_legacy as this was
added specifically for building on qemu_cortex_m3.

Signed-off-by: Kumar Gala <kumar.gala@intel.com>