refactor: validate_and_update_canister_settings

[mraszyk]

Refactored CanisterManager to eliminate the validate/apply split for canister settings by merging both functions into a single validate_and_update_canister_settings function that validates and mutates in one pass, removing all .expect() panics.

This is possible now that

• changing canister settings operates on a clone of canister state and round limits; and
• canister creation only commits the canister state upon success and operates on a clone of round limits (the latter was changed in this PR).

[Copilot]

Pull request overview

This PR refactors canister settings handling in the execution environment by removing the previous “validate then apply” split and instead validating + mutating canister settings in a single pass, with the intent of eliminating .expect() panics and relying on cloned state / rollback for failure cases.

Changes:

• Removed ValidatedCanisterSettings and the separate validate_* / do_update_settings() pipeline, replacing it with validate_and_update_canister_settings() that mutates CanisterState and RoundLimits directly.
• Updated canister creation flow to snapshot and restore round_limits on failure, and added a regression test for reverting subnet available memory when creation fails mid-way.
• Adjusted update_settings to use the new combined validate+apply flow.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
rs/execution_environment/src/canister_settings.rs	Removes the now-obsolete ValidatedCanisterSettings type.
rs/execution_environment/src/canister_manager.rs	Replaces validate/apply split with a combined validate+mutate function; updates update/create flows accordingly.
rs/execution_environment/src/canister_manager/tests.rs	Adds a test ensuring subnet available memory is reverted when canister creation fails after partial resource updates.

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[Copilot]

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 2 comments.

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[Copilot]

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated no new comments.

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[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated no new comments.

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