Studies of $${\mathrm {B}} ^{*}_{{\mathrm {s}}2}(5840)^0 $$ and $${\mathrm {B}} _{{\mathrm {s}}1}(5830)^0 $$Bs1(5830)0 mesons including the observation of the $${\mathrm {B}} ^{*}_{{\mathrm {s}}2}(5840)^0 \rightarrow {\mathrm {B}} ^0 \mathrm {K} ^0_{\mathrm {S}} $$→B0KS0 decay in proton-proton collisions at $$\sqrt{s}=8\,\text {TeV} $$s=8TeV