fix: reduce Sales Invoice row size (backport #27136)

[mergify]

Sales Invoice doctype is starting to hit row length limit as many integrations add custom fields on this doctype. This is just a small change to remove VARCHAR(140) fields and reduce row size wherever possible.

Changes:

1. Where max length is known set it instead of default which is 140. E.g. Select type and "Scan Barcode" (which is a dummy field)
2. Change Data to Small Text where field is only used for reference like customer name, amount in words.

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   This is an automatic backport of pull request fix: reduce Sales Invoice row size #27136 done by Mergify.

[mergify]

Cherry-pick of 8d116fb has failed:

On branch mergify/bp/version-13-hotfix/pr-27136
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	both modified:   erpnext/accounts/doctype/sales_invoice/sales_invoice.json

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