[roll] Roll fuchsia [syslog] Allow setting severity from an env var.

Allow host tests and tools to have their log severity
set by their callers. Should make it easier to debug
cross-tool interactions without having to wire up command
line changes for all tools involved.

Can only ever decrease the minimum severity level, never
increases it. For example this means that if a program
explicitly asks for DEBUG level logs it won't have its
environment override them to INFO level.

Original-Bug: 359658592
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1152712
Original-Revision: 6d9abb19c5239d49b9e5124d22b6c26620139eab
GitOrigin-RevId: b0dbad28bf0c096c0dfdf15254b9e6d4d4d68e2b
Change-Id: I48941ec992403547a2bea8d887e65cbf0466217d

Author: Adam Perry

stem

@@ -11,7 +11,7 @@
              githooks="integration/git-hooks"
              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="3962f3f451686e417ee18de2dc5cb13944e41837"/>
+             revision="6d9abb19c5239d49b9e5124d22b6c26620139eab"/>
   </projects>
   <hooks>
     <hook name="install-environment"