Support fourmolu 0.13

[brandonchinn178]

Includes the revert from #3661. Feel free to merge into one PR. cc @joyfulmantis

Tested with the following script:

(
    set -e
    function test_fourmolu() {
        local constraint="fourmolu$1"
        echo "#### $constraint"
        cabal test \
            -w "$2" \
            --constraint "$constraint" \
            --index-state HEAD \
            hls-fourmolu-plugin
    }
    test_fourmolu '==0.13.0.0' 'ghc-9.6.1'
    test_fourmolu '<0.13' 'ghc-9.6.1'
    test_fourmolu '<0.8.1' 'ghc-9.2.7'
    test_fourmolu '<0.7' 'ghc-9.2.7'
)

---

Note: I noticed the tests sometimes flakily fail with

Could not access 'plugins/hls-fourmolu-plugin/test/testdata/test/testdata/Fourmolu2.formatted.hs'

Not sure what's happening, and why the test directory is repeated.

[brandonchinn178]

This seems to have been testing the wrong file for quite a while:
f653555#diff-5e783ba6072f1ca27c7171a3ece5043ea46f212e57f68272b52ecc36a8152d59L26-L36