bundle2: make server.bundle2.stream default to True Support for bundle2 streaming clones has been shipped in Mercurial 4.5 (7eedbd5d4880), but was never activated by default. It's time to have more people use it. The new format allows streaming clones to transport cache (hooray for speed) and phaseroots (fixes phase-related issues). Changes in tests: bundle2 capabilities now have "stream=v2" (plus a '\n' as a separator) and therefore take 14 bytes more: "%0Astream%3Dv2". Tip for tests that have data encoded with CBOR: 0xd3 - 0xc5 = 14. $USUAL_BUNDLE2_CAPS$ replaces $USUAL_BUNDLE2_CAPS_SERVER$, which is the same thing, but without "stream=v2". Since streaming clones now also transfer caches, the reported byte and file counts are higher (e.g. 816 bytes in 9 files instead of 613 bytes in 4 files, a bit of --debug and manual math confirms that the caches take these extra 203 bytes in 5 files). Differential Revision: https://phab.mercurial-scm.org/D4680