[Refactor] - Rename the `upperCaseVariantName` to `titleCaseVariantName`

[hurali97]

Description:

Currently in the gradle-plugins/react/brownfield we have some variables named upperCaseVariantName. However, they do not really reflect an upper case variant, rather they reflect a Title Case variant.

An example below:

react-native-brownfield/gradle-plugins/react/brownfield/src/main/kotlin/com/callstack/react/brownfield/processors/VariantProcessor.kt

Line 29 in e854a2f

private val upperCaseVariantName = variant.name.replaceFirstChar(Char::titlecase)

With this issue and the corresponding PR, we would like to replace all the instances of upperCaseVariantName to titleCaseVariantName

[artus9033]

Closed with #165