rust: Return HgError instead of RevlogError in revlog constructors
This leaves fewer cases for callers to handle, as RevlogError is more general
Differential Revision: https://phab.mercurial-scm.org/D11410
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"phabricator.uri": "https://phab.mercurial-scm.org/",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}