use same calculation as CDPManager for CDP split fee in invariant test

[rayeaster]

• use the same calculation for CDP fee split as in CDPManagerStorage.sol#getAccumulatedFeeSplitApplied()
• compare the raw value in CDP before and after rebase

[getrecon-bot]

Job ID	e6473295-6b50-4361-9ac0-e0af4f57ed4f
Command	yarn && git submodule init && git submodule update && solc-select use 0.8.17 && cd packages/contracts/ && yarn echidna --test-mode assertion --test-limit 300000
Instance ID	i-05ec76d62276c0a2b
Instance Type	c5.2xlarge
Status	Started
Elapsed

[getrecon-bot]

Job ID	e6473295-6b50-4361-9ac0-e0af4f57ed4f
Command	yarn && git submodule init && git submodule update && solc-select use 0.8.17 && cd packages/contracts/ && yarn echidna --test-mode assertion --test-limit 300000
Instance ID	i-05ec76d62276c0a2b
Instance Type	c5.2xlarge
Status	Running
Elapsed	1 minute 18 seconds

[getrecon-bot]

Job ID	e6473295-6b50-4361-9ac0-e0af4f57ed4f
Command	yarn && git submodule init && git submodule update && solc-select use 0.8.17 && cd packages/contracts/ && yarn echidna --test-mode assertion --test-limit 300000
Instance ID	i-05ec76d62276c0a2b
Instance Type	c5.2xlarge
Status	Running
Elapsed	1 minute 19 seconds

[getrecon-bot]

Job ID	e6473295-6b50-4361-9ac0-e0af4f57ed4f
Command	yarn && git submodule init && git submodule update && solc-select use 0.8.17 && cd packages/contracts/ && yarn echidna --test-mode assertion --test-limit 300000
Instance ID	i-05ec76d62276c0a2b
Instance Type	c5.2xlarge
Status	Success
Elapsed	18 hours 6 minutes 18 seconds