Set the max PoV size

[nakul1010]

Is your feature request related to a problem? Please describe.
Currently the MAXIMUM_BLOCK_WEIGHT -> proof_size parameter is taken from cumulus_primitives here which is used in frame_system::Config::BlockWeight. But the proof_size should depend on interlays para chain block fullness.

Describe the solution you'd like
Needs to be discussed.

Additional context

• Originally added as a comment in PR feat: update dependencies to polkadot v1 release #1149
• Parity's PR 13958
• PoV definition.