Use unusual strings in E2E test suite

What does this MR do?

Adds the following to branch names: /, \, #, --, ", ; and UPPERCASE spelling

Adds the following to file names: /, #, :, ?a=b&c=d, -start-with-dash

Primarily addresses the past regression connected to slashes and hashes in branch names but also covers a few unusual strings mentioned in https://gitlab.com/cirosantilli/test.

See gitlab-com/www-gitlab-com#7228 (closed) for more details.

NB I considered inserting such strings at the resource fabrication level, but decided against it - if there is an issue with the name we are likely to lose coverage in multiple tests at once so it poses a significant risk. Therefore strings were modified at a test level. Interestingly enough, there is an existing ProtectedBranch resource that has a slash in the default branch name, however it is never used as all tests with protected branches set this value (I did insert a slash in one of them).

Does this MR meet the acceptance criteria?

Conformity

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