Create CMIP7 version of `recipe_seaice_sensititvity.yml`

[NParsonsMO]

Fake dataset:
- {activity: CMIP, project: CMIP7, exp: historical, dataset: UKCM2-0-LL, institute: MOHC, ensemble: r1i1p1f3, exp: 1pctCO2, grid: g100, label_dataset: True}

Change time period:
end_year now 2021 (but testing with different dates for available fake data)

Change variables:

    variables:
      siconc:
        preprocessor: pp_arctic_sept_sea_ice
        realm: &siconc_realm seaIce
        mip: *siconc_realm
        frequency: mon
        region: glb
        branding_suffix: tavg-u-hxy-u
      tas: &tas
        preprocessor: pp_avg_ann_global_temp
        realm: &tas_realm atmos
        mip: *tas_realm
        frequency: mon
        region: glb
        branding_suffix: tavg-h2m-hxy-u

(and equivalent for antarctic)

New section in my user config

projects:
  CMIP7:
    data:
      local:
        type: esmvalcore.io.local.LocalDataSource
        rootpath: /my/data/dir/fake_cmip7_data
        dirname_template: "{project}/{activity}/{institute}/{dataset}/{exp}/{ensemble}/{region}/{frequency}/{short_name}/{branding_suffix}/{grid}/{version}"
        filename_template: "{short_name}_{branding_suffix}_{frequency}_{region}_{grid}_{dataset}_{exp}_{ensemble}*.nc"

[NParsonsMO]

File tree within fake_cmip7_data

.
└── CMIP7
    └── CMIP
        └── MOHC
            └── UKCM2-0-LL
                └── 1pctCO2
                    └── r1i1p1f3
                        └── glb
                            ├── fx
                            │   ├── areacella
                            │   │   └── ti-u-hxy-u
                            │   │       └── g100
                            │   │           └── v20260511
                            │   │               └── areacella_ti-u-hxy-u_fx_glb_g100_UKCM2-0-LL_1pctCO2_r1i1p1f3.nc
                            │   └── areacello
                            │       └── ti-u-hxy-u
                            │           └── g100
                            │               └── v20260511
                            │                   └── areacello_ti-u-hxy-u_fx_glb_g100_UKCM2-0-LL_1pctCO2_r1i1p1f3.nc
                            └── mon
                                ├── siconc
                                │   └── tavg-u-hxy-u
                                │       └── g100
                                │           └── v20260511
                                │               └── siconc_tavg-u-hxy-u_mon_glb_g100_UKCM2-0-LL_1pctCO2_r1i1p1f3_190001-190912.nc
                                └── tas
                                    └── tavg-h2m-hxy-u
                                        └── g100
                                            └── v20260511
                                                └── tas_tavg-h2m-hxy-u_mon_glb_g100_UKCM2-0-LL_1pctCO2_r1i1p1f3_189901-190912.nc