feat(--gas-report): add option to include tests

[grandizzy]

Motivation

Closes #6129
#6129 (comment)
add gas_reports_include_tests = true config to include tests in gas report

Solution

[zerosnacks]

Reasonable change, for simplicity I think include_tests is OK but we likely want to document that the gas report will include all of the following:

/// Test function kind.
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
pub enum TestFunctionKind {
    /// `setUp`.
    Setup,
    /// `test*`. `should_fail` is `true` for `testFail*`.
    UnitTest { should_fail: bool },
    /// `test*`, with arguments. `should_fail` is `true` for `testFail*`.
    FuzzTest { should_fail: bool },
    /// `invariant*` or `statefulFuzz*`.
    InvariantTest,
    /// `afterInvariant`.
    AfterInvariant,
    /// `fixture*`.
    Fixture,
}

[grandizzy]

Reasonable change, for simplicity I think include_tests is OK but we likely want to document that the gas report will include all of the following:

was thinking include_tests more of a include test contracts rather than functions (as at the end they're all grouped per contract in report). Can detail this in book when updated with new option, would this work?