Y24-402 - Specify 'no. pools' rather than 'no. samples per pool' in submission

[KatyTaylor]

User story
As a user of the scRNA Core cDNA Prep pipeline, I would like the customer to be able to specify the 'number of pools' at a study-project level in the cDNA Prep submission (bulk submission interface only). This is instead of the 'number of samples per pool', which was added here.

Who are the primary contacts for this story
Katy, Abby

Who is the nominated tester for UAT
Abby

Acceptance criteria
To be considered successful the solution must allow:

• cDNA Prep bulk submission has column for 'number of pools'
• cDNA Prep bulk submission does not have column for 'number of samples per pool'
• 'Number of pools' must not vary within a study-project group (equivalent validation for existing fields is being done here).
• 'Number of pools' must be between 2 and 8 (inclusive).
• 'Number of samples per pool' (to be calculated - see additional context) must be between 5 and 25 (inclusive), for each pool (number could vary by 1 between pools).

References
This will be used in sanger/limber#1985, but they could be done in either order as long as the request metadata migration is done as part of whichever one comes first.

The 'number of samples per pool' field added to request_metadata as part of #4337 is now obsolete - so we could change the name of this field rather than adding a new one?

Additional context
To calculate 'Number of samples per pool' from 'Number of pools' for a study-project group, see the method used by Abby's spreadsheet here -
cDNA Prep Submission Pooling Strategy.xlsx

We won't use this spreadsheet directly - this is just to illustrate how to do the calculation.