[tor-bugs] #31625 [Core Tor/Tor]: config refactoring: fix hierarchy of configuration variable flags

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#31625: config refactoring: fix hierarchy of configuration variable flags
-----------------------------------------+---------------------------------
 Reporter:  nickm                        |          Owner:  nickm
     Type:  defect                       |         Status:  accepted
 Priority:  Medium                       |      Milestone:  Tor:
                                         |  0.4.2.x-final
Component:  Core Tor/Tor                 |        Version:
 Severity:  Normal                       |     Resolution:
 Keywords:  network-team-roadmap-august  |  Actual Points:
Parent ID:  #29211                       |         Points:  .5
 Reviewer:  teor                         |        Sponsor:
-----------------------------------------+---------------------------------

Comment (by nickm):

 I'm afraid this one is a larger branch than I thought it would be, but the
 individual commits should be very simple.  (The overall diff is not too
 small either).  Please let me know if you would like me to split it up.

 The branch is currently divided into these parts:

 1. Change the accessor functions in confparse.c so that they correspond to
 the low-level properties that we want to check.
 {{{
       config: replace config_var_is_cumulative with is_replaced_on_set()
       config: Invert sense of _is_invisible, and rename to is_listable()
       Document config_var_is_dumpable and config_var_is_settable.
       config: Introduce the concept of an "ungettable" variable.
       config: rename "contained" to "derived", and explain it better.
       config: make config_var_is_dumpable static.
 }}}

 2. Change the booleans in var_type_def_t into bit flags:
 {{{
       struct_var: refactor struct_var_is*() functions to delegate
       typed_var: Make flags into an unsigned OR of bits.
       Move VTFLAG_* declarations to conftypes.h
       Re-number VTFLAG_* values so they don't conflict with CVFLAG_*
 }}}

 3. Replace the old flags with the new ones:
 {{{
       Replace low-level {var_type,struct_var}_is_*() with flag inspection
       confparse, conftypes: Replace flags with their new names.
       Remove all VTFLAG_* usage.
       Remove all CVFLAG_* usage.
       Revise documentation on CFLG_* flags
       Changes file for 31625 (config flag refactor)
 }}}

 Right now I am running it on CI to see what the coverage looks like.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/31625#comment:8>
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