Change hardcoded tests into fuzztests.

[a-t-0]

Where possible, change the tests from hardcoded tests, to fuzztests with random variables over ranges. For example see: https://book.getfoundry.sh/forge/fuzz-testing

• Visualise the hit rate of each branch in the fuzz test.
• Assert each branch of the fuzz test is hit.
• Write a test that is able to generate arbitrary tiers.
• Restore Slither by including the ViaIR=true in the json or the --via-ir flag in the CLI via precommit.
• Create expect reverts for runs in which the initialisation is not valid.
• Merge can Initialise and initialise by returning a boolean, and the actual object or dummy object as tupple.
• Move getRandomMultiplesAndCeilings into a separate file and import the constants from somewhere. #25
• Find out how to exclude initialisation function from coverage but how to include consequtive function that is called.
• Find out how to visualise the test case ratio through emit log.
• randomize number of investments. #27

[a-t-0]

// Assume requirements on contract initialisation by project lead are valid.
    // vm.assume(projectLeadFracDenominator > 0);
    // vm.assume(firstCeiling > 0);
    // vm.assume(additionalWaitPeriod > 0);
    // vm.assume(raisePeriod > 0);
    // vm.assume(investmentTarget > 0);
    // vm.assume(firstCeiling < secondCeiling);
    // vm.assume(secondCeiling < thirdCeiling);
    // vm.assume(investmentTarget <= thirdCeiling);
    // vm.assume(projectLeadFracNumerator <= projectLeadFracDenominator);
    // vm.assume(firstMultiple > 1);
    // vm.assume(secondMultiple > 1);
    // vm.assume(thirdMultiple > 1);

    // Assume an investor tries to invest at least 1 wei.
    // vm.assume(firstInvestmentAmount > 0);
    
    // Store multiples in an array to assert they do not lead to an overflow when computing the investor return.
    // uint8[] memory multiples = new uint8[](3);
    // multiples[0] = firstMultiple;
    // multiples[1] = secondMultiple;
    // multiples[2] = thirdMultiple;
    // vm.assume(!_testHelper.sumOfNrsThrowsOverFlow({ numbers: multiples }));
    // vm.assume(
    // !_testHelper.yieldsOverflowMultiply({
    // a: firstMultiple + secondMultiple + thirdMultiple,
    // b: firstInvestmentAmount
    // })
    // );