Staking: Add deprecate_controller_batch AdminOrigin call

[rossbulat]

Partially Addresses #2500

Adds a deprecate_controller_batch call to the staking pallet that is callable by Root and StakingAdmin. To be used for controller account deprecation and removed thereafter. Adds MaxControllersDeprecationBatch pallet constant that defines max possible deprecations per call.

• Add deprecate_controller_batch call, and MaxControllersInDeprecationBatch constant.
• Add tests, benchmark, weights. Tests that weight is only consumed if unique pair.
• Adds StakingAdmin origin to staking's AdminOrigin type in westend runtime.
• Determined that worst case 5,900 deprecations does fit into maxBlock proofSize and refTime in both normal and operational thresholds, meaning we can deprecate all controllers for each network in one call.

Block Weights

By querying consts.system.blockWeights we can see that the deprecate_controller_batch weights fit within the normal threshold on Polkadot.

controller_deprecation_batch where i = 5900:

Ref time: 69,933,325,300

Proof size: 21,040,390

Polkadot

// consts.query.blockWeights

maxBlock: {
        refTime: 2,000,000,000,000
        proofSize: 18,446,744,073,709,551,615
}
normal: {
 maxExtrinsic: {
	refTime: 1,479,873,955,000
	proofSize: 13,650,590,614,545,068,195
 }
 maxTotal: {
	refTime: 1,500,000,000,000
	proofSize: 13,835,058,055,282,163,711
 }
}

Kusama

// consts.query.blockWeights

  maxBlock: {
    refTime: 2,000,000,000,000
    proofSize: 18,446,744,073,709,551,615
  }
    normal: {
      maxExtrinsic: {
        refTime: 1,479,875,294,000
        proofSize: 13,650,590,614,545,068,195
      }
      maxTotal: {
        refTime: 1,500,000,000,000
        proofSize: 13,835,058,055,282,163,711
      }
}

[rossbulat]

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[command-bot]

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