BaseVaultTest refactoring

[elshan-eth]

Description

This PR makes variables that are used as constants actually constant and also adds some hooks for more flexible lifecycle customization.

Type of change

• Bug fix
• New feature
• Breaking change
• Dependency changes
• Code refactor / cleanup
• Optimization: [ ] gas / [ ] bytecode
• Documentation or wording changes
• Other

Checklist:

• The diff is legible and has no extraneous changes
• Complex code has been commented, including external interfaces
• Tests have 100% code coverage
• The base branch is either main, or there's a description of how to merge

Issue Resolution

[EndymionJkb]

Such a big diff I might have missed something, but looks good. Could perhaps have done the lifecycle stuff separately as a small PR, but I guess it's fine

[EndymionJkb]

There are several similar functions here that are identical except for the target of the loop. Consider factoring it out into BaseVaultTest (maybe with an argument for the array). For instance, BigWeightedPool.t.sol's _approvePoolTokensForSender / _approvePoolTokensForPool; and here _approveNewPoolForSender / _approveForNewPool

[EndymionJkb]

I think these can all be constant.

Suggested change

	uint256 internal DEFAULT_AMOUNT_ROUND_DOWN = DEFAULT_AMOUNT - 2;
	// Default amount of BPT to use in tests for user operations.
	uint256 internal DEFAULT_BPT_AMOUNT = 2e3 * 1e18;
	// Default amount of BPT round down.
	uint256 internal DEFAULT_BPT_AMOUNT_ROUND_DOWN = DEFAULT_BPT_AMOUNT - 2;
	// Default rate for the rate provider mock.
	uint256 internal DEFAULT_MOCK_RATE = 2e18;
	// Default swap fee percentage.
	uint256 internal DEFAULT_SWAP_FEE_PERCENTAGE = 1e16; // 1%
	// Default protocol swap fee percentage.
	uint64 internal DEFAULT_PROTOCOL_SWAP_FEE_PERCENTAGE = 50e16; // 50%
	uint256 internal constant DEFAULT_AMOUNT_ROUND_DOWN = DEFAULT_AMOUNT - 2;
	// Default amount of BPT to use in tests for user operations.
	uint256 internal constant DEFAULT_BPT_AMOUNT = 2e3 * 1e18;
	// Default amount of BPT round down.
	uint256 internal constant DEFAULT_BPT_AMOUNT_ROUND_DOWN = DEFAULT_BPT_AMOUNT - 2;
	// Default rate for the rate provider mock.
	uint256 internal constant DEFAULT_MOCK_RATE = 2e18;
	// Default swap fee percentage.
	uint256 internal constant DEFAULT_SWAP_FEE_PERCENTAGE = 1e16; // 1%
	// Default protocol swap fee percentage.
	uint64 internal constant DEFAULT_PROTOCOL_SWAP_FEE_PERCENTAGE = 50e16; // 50%