Go: Handle quoted dots in hostname regexps

[theinfosecguy]

go/incomplete-hostname-regexp reports literal hostname dots inside Go's \Q...\E quoting as wildcards. For example, ^\Qhttps://github.com/\E$ produces a false positive.

Recognize quoted dots when the complete pattern is statically known. Preserve existing alerts for wildcard dots outside quoting and unsafe concatenations with escaped quote openers, and retain existing behavior for unresolved patterns.

Add regressions for raw and interpreted strings, quoting boundaries, constant aliases, and regexp compilation and matching APIs, plus a change note.

Validation:

• All four Go CWE-020 query-test suites pass with CodeQL 2.27.0.
• The new quoting fixture covers 13 unsafe operations and 11 safe operations.
• QL formatting and git diff --check pass.

Fixes #15894.