Is namaz e wahshat a community namaz to be performed by everyone or is to be performed only by the wali of the mayyat.

None of the prayers which has been recommended (but are not wajib) have no such ruling. So Namaz Wahshat e Qabr also cannot be a community namaz but if anyone wants to offer is send Sawab to the Marhoom can offer but Ayatullah Sistani (May Allah protect him) says that in case of other that Marhooms relatives he/she should do “Niyyat of Reja e Matloob” (May Allah accept it) not Mustahab. Please listen this:

https://youtu.be/nrPKXwygGAU