feat: introduce getQueriesForElement as alias for within.

[mdjastrzebski]

Describe the Feature

TL/RN v6 has provided getQueriesForElement for scoping queries to given element & it's children. RNTL v2 had a similar within function. Both of these were modeled on similar RTLs helper. In RTL both names are available (as alias) to provide the same function.

Possible Implementations

Provide getQueriesForElement as alias to within.

Benefits

• compatibility with RTL
• easier migration path for TL/RN v6 users.

Related Issues

Migration to v7, #456

[mdjastrzebski]

CC: @thymikee, @cross19xx, @Esemesek

[thymikee]

This is a simple rename and I've already created a migration doc for it: https://github.com/callstack/react-native-testing-library/pull/456/files#diff-e96d057ee0b5c209da93af10f6a373c1R51-R54

On the other hand, DOM testing library has this alias as well. Feel free to contribute this, but I'd prefer focusing more on the migration guide.

[thymikee]

Closed via #461