v2.1: SIMD-0207: Raise block limit to 50M (backport of #4026)

[mergify]

Problem

• SIMD-0207: Raise Block Limits to 50M solana-foundation/solana-improvement-documents#207

Summary of Changes

• Add feature to the feature set for raising block limits
• Clean up old limit justification(s)
• Add function to get new limits for SIMD-0207
• Add feature-activation path for SIMD-0207

Fixes #

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This is an automatic backport of pull request #4026 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of ccb3cd3 has failed:

On branch mergify/bp/v2.1/pr-4026
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You are currently cherry-picking commit ccb3cd3a7.
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Changes to be committed:
	modified:   cost-model/src/cost_tracker.rs
	modified:   runtime/src/bank/tests.rs

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   cost-model/src/block_cost_limits.rs
	both modified:   runtime/src/bank.rs
	both modified:   sdk/feature-set/src/lib.rs

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally