Added initial PNA support into p4c.

[rupesh-chiluka-marvell]

To add PNA support into the bmv2 backend. Leveraging the psa_switch as the foundation, the pna_nic has been developed.

A basic L2 forward PNA p4 program has been compiled with the updated P4 compiler (p4c-bm2-pna). Basic L2 Forward test has been carried out.

[vlstill]

(I've unlocked the CI which is blocked for outside contributors by default)

[fruffy]

Thank you for your contribution! This seems really interesting and useful.

The first step here is to fix the compilation errors in CI.

[rupesh-chiluka-marvell]

Ok, Will do that.