Change default perspective selection logic

[zsoltkebel]

Description of work

Slight modification of default perspective selection. Now you can easily change "landing" view by changing the default perspective id constant in PerspectivesProvider.

Ticket

ISISComputingGroup/IBEX#7403 (comment)

Acceptance criteria

• No content change.

Unit tests

Small change

System tests

Small change

Documentation

Small change

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Code Review

• Is the code of an acceptable quality?
• If the change is to an OPI, does the check_opi_format.py script in C:\Instrument\Dev\ibex_gui\base\uk.ac.stfc.isis.ibex.opis pass?
• Do the changes function as described and is it robust?
• Is there associated PR for the release notes?

Final Steps

• Reviewer has also merged the release notes