Rename FormField Value() to getFormattedValue()

[emteknetnz]

Split off from #11449 (comment)

FormField::getValue() was added in #11422 when implementing FieldValidation on FormFields

getValue() is confusing alongside Value() which should really be called getFormattedValue() as the method will often return a formatted version $this->value, which seems like it's intended for use within templates. It also looks like it's used a lot inside FormFields as $this->Value(), $this->getValue() should probably be used instead.

Acceptance criteria

• Rename FormField::Value() to FormField::getFormattedValue()
• Update FormFIeld code that used $this->Value() to use $this->getValue() instead where appropriate
• Check templates and use $FormattedValue instead of $Value
• Changelog calls out that projects and modules will need to update their templates

CMS 5 PRs

• API Deprecate FormField Value #11551
• DOC Deprecate FormField Value developer-docs#671

CMS 6 Kitchen Sink CI

• https://github.com/creative-commoners/recipe-kitchen-sink/actions/runs/13068510624

CMS 6 PRs

• API Rename FormField Value to getFormattedValue silverstripe-elemental#1306
• API Rename FormField Value to getFormattedValue silverstripe-admin#1888 (approved)
• API Rename FormField Value to getFormattedValue silverstripe-asset-admin#1536 (approved)
• API Rename FormField Value to getFormattedValue silverstripe-cms#3049 (approved)
• API Rename FormField Value to getFormattedValue #11550
• API Rename FormField Value to getFormattedValue silverstripe-frameworktest#224 (approved)
• API Rename FormField Value to getFormattedValue silverstripe-linkfield#362 (approved)
• API Rename FormField Value to getFormattedValue silverstripe-realme#175 (approved)
• API Rename FormField Value to getFormattedValue silverstripe-subsites#626 (approved)
• API Rename FormField Value to getFormattedValue silverstripe-tagfield#317
• API Rename FormField Value to getFormattedValue silverstripe-userforms#1363 (approved)
• API Rename FormField Value to getFormattedValue silverstripe-versioned-admin#385
• API Rename FormField Value to getFormattedValue symbiote/silverstripe-advancedworkflow#567 (approved)
• API Rename FormField Value to getFormattedValue symbiote/silverstripe-gridfieldextensions#425 (approved)
• API Rename FormField Value to getFormattedValue tractorcow-farm/silverstripe-fluent#918 (approved)
• DOC Rename FormField method developer-docs#670

[GuySartorelli]

Trying a new thing with my review on this - lemme know if the (approved) next to the PR links is useful.