Support Drupal core versions that were not released yet

[shaal]

Is your feature request related to a problem? Please describe

Cannot test Drupal 10.0.x, because it wasn't published through Packagist yet (cannot get drupal/core-recommended:^10)

Describe the solution you'd like

For core issues, we can separate DP_MODULE_VERSION (ie. 10.0.x which is fetched from the issue page)
and DP_CORE_VERSION (ie. 9.3.x which is chosen by user, according to what's available through browser extension)

Composer require drupal/core-recommended, can use DP_CORE_VERSION, and symlink repos/drupal of version 10 (through DP_MODULE_VERSION)

Example of an issue - https://www.drupal.org/project/drupal/issues/3251891

DrupalPod browser extension generated URL -
https://gitpod.io/#DP_PROJECT_NAME=drupal,DP_ISSUE_FORK=,DP_ISSUE_BRANCH=,DP_PROJECT_TYPE=project_core,DP_MODULE_VERSION=10.0.x,DP_CORE_VERSION=9.3.x,DP_PATCH_FILE=https%3A%2F%2Fwww.drupal.org%2Ffiles%2Fissues%2F2021-11-30%2F3251891.patch,DP_INSTALL_PROFILE=demo_umami/https://github.com/shaal/drupalpod

Describe alternatives you've considered

Additional context