Global Attributes in output files

### Are there any linked Issues or Pull Requests?

_No response_

### Brief description

LFRic, using XIOS writes a set of global attributes into output files, e.g.:
```CF
// global attributes:
:name = "results/lfric_diagnostics" ;
:description = "Created by xios" ;
:title = "Created by xios" ;
:Conventions = "UGRID" ;
:timeStamp = "2026-Apr-07 11:07:27 GMT" ;
:uuid = "03533c65-d239-44cc-90f4-26ada01a1f05" ;

```
providing metadata that is applicable to the whole file and all data variables within it.
this forms part of the data identity.

The many per-file `global attributes` can limit Iris `cubes` from merging across files, such as "timeStamp", "uuid", "name", "source", "analysis_source", and "history".
Should these at least be consistent between files from the same run?

There is a balance here between what is identifying metadata that is important / useful for the raw model output, and what is limiting in terms of managing data across many files.

This issue shall explore this topic and propose a coherent change set to `global_attribute` metadata if appropriate.

Essentially a trade off between:
1. providing identifying metadata in the files via UUID & timeStamp, which can be deemed useful
* this then requires processing knowledge, e.g. writing iris call back functions to strip this on load
1. removing identifying metadata in the files, such as UUID & timeStamp
* making Iris loading easier, but losing some identification information that may be useful in other scenarios (e.g. archive data management)

### Further details of the issue.

_No response_