status: make 'hg status --rev' faster when there are deleted files In order not to avoid listing files as both added and deleted, for example, we check for every file in the manifest if it is in the _list_ of deleted files. This can get quite slow when there are many deleted files. Change it to a set to make the containment check faster. On a somewhat contrived example of the Mozilla repo with the entire testing/ directory deleted (~14k files), this makes 'hg status --rev .^' go from 26s to 2s.

setdiscovery: limit the size of the initial sample (issue4411) The set discovery start by sending a "known" command with all local heads. When the number of local heads is massive (eg: using hidden changesets) such request becomes too large. This lead to 414 error over http, aborting the whole process. We limit the size of the sample used by the first query to fix this. The test are impacted because they do test massive number of heads. But they do not test it over real world http setup.

setdiscovery: extract sample limitation in a `_limitsample` function We need to reuse this logic for the initial query. We extract it in a function to unsure sample limiting is applied consistently in all cases.