CMIP7: UKESM1-3-LL: Investigate missing longitude bounds for ond_ocean-native-grid-T

During testing for UKESM1-3-LL. No variables within the ond/grid-T ocean_native stream could be produced and gave the error:
`Unable to produce MIP requested variable : The MIP requires that bounds exist for the axis "longitude", but unable to guess bounds as the coordinate is not 1D`

This error affects the following variables and was triggered using the model UKESM1-3-LL, workflow u-dw498 and experiment esm-piControl. Please contact myself for the specific request file.

| Variable | Realm | Variable information |
| ----- | ----- | ----- |
| sos_tavg-u-hxy-sea | CMIP7_ocean | [1338](https://github.com/UKNCSP/CDDS-CMIP7-mappings/issues/1338) |
| tos_tavg-u-hxy-sea | CMIP7_ocean | [1340](https://github.com/UKNCSP/CDDS-CMIP7-mappings/issues/1340) |
| zos_tavg-u-hxy-sea | CMIP7_ocean | [1348](https://github.com/UKNCSP/CDDS-CMIP7-mappings/issues/1348) |
| mlotst_tavg-u-hxy-sea | CMIP7_ocean | [748](https://github.com/UKNCSP/CDDS-CMIP7-mappings/issues/748) |
| tossq_tavg-u-hxy-sea | CMIP7_ocean | [1341](https://github.com/UKNCSP/CDDS-CMIP7-mappings/issues/1341) |
| so_tavg-ol-hxy-sea | CMIP7_ocean | [1337](https://github.com/UKNCSP/CDDS-CMIP7-mappings/issues/1337) |
| t20d_tavg-u-hxy-sea | CMIP7_ocean | [786](https://github.com/UKNCSP/CDDS-CMIP7-mappings/issues/786) |

Start with the ond/grid-T ocean_native stream and reproduce the failure using UKESM1-3-LL, workflow u-dw498, and experiment esm-piControl; request the specific request file from the reporter. Check how longitude bounds are handled for the listed variables. Done means identifying the cause and validating a resolution that allows these variables to be produced without the non-1D longitude error.

Written by the indexing model from the issue text.