tests: add the sqlite revmap test The SqliteRevMap test generates new tests based on existing tests. The generated tests will use SqliteRevMap instead of RevMap. Tests are selected if they are both interesting and fast. For comprehensive tests like rebuildmeta and updatemeta, only a few svndumps are selected. On my laptop vm, the sqlite revmap test completes within 6.2s. Note: the current way tests are running will not gc the database connections well, meaning it can leak fd. Fortunately it's only 55 tests now. If we add a lot more tests in the future, be aware of the fd leak issue.