Rename default branch of repo ide-urls from master to main

[mvomiero]

• Rename default branch of repo ide-urls https://github.com/devonfw/ide-urls/branches from master to main
• Change branch name in code, introducing a constant instead of a variable: https://github.com/devonfw/IDEasy/blob/81bb8bbe4262645b83cec11c0490afb5991a34b1/cli/src/main/java/com/devonfw/tools/ide/context/GitContextImpl.java#L77

[hohwille]

While this sounds like a good idea, the first suggested point IMHO will break devonfw-ide. For the second point my thoughts are:

• hardcoding "master" here is really a bug and does not make any sense. It has to be changed to branch. I must have missed this in the review.
• for ide-urls we can actively pass "master" as branch argument if we use the pullOrCloneAndResetIfNeeded after all.
• or as alternative for the previous point we can determine the default branch properly via git if it was not explicitly provided as argument (null was given for branch what typically only should happen from delegation of methods with the same name but lacking the branch parameter).

[hohwille]

For the ide-urls repo and the main vs. master branch, we should create a separate issue. What we could do is copy (instead of rename) the master branch to main. We could also test locally somehow with devonfw-ide if nothing breaks if the default branch gets changed (e.g. by changing the hardcoded URL to some fork where we test this in advance). Test must cover both initial setup as well as updates (devon ide update).