rust-revlog: don't create an in-memory nodemap for filelogs from Python
Explanations inline.
Benchmarks from this change affect positively the only repo that showed this
being a problem:
```
### data-env-vars.name = mozilla-try-2024-03-26-ds2-pnm
# benchmark.name = hg.command.cat
# bin-env-vars.hg.flavor = rust
# bin-env-vars.hg.py-re2-module = default
# benchmark.variants.files = all-root
# benchmark.variants.output = plain
# benchmark.variants.rev = tip
default: 62.848869 ~~~~~
before-this-patch: 58.113051 (-7.54%, -4.74)
this-patch: 57.407533 (-8.66%, -5.44)
### data-env-vars.name = mozilla-try-2024-03-26-ds2-pnm
# benchmark.name = hg.command.log
# bin-env-vars.hg.flavor = rust
# bin-env-vars.hg.py-re2-module = default
# benchmark.variants.limit-rev = 10
# benchmark.variants.patch = yes
# benchmark.variants.rev = none
default: 3.173532 ~~~~~
before-this-patch: 3.543591 (+11.66%, +0.37)
this-patch: 3.297235 (+3.90%, +0.12)
```
#!/usr/bin/env python3
#
# An example hgweb CGI script, edit as necessary
# See also https://mercurial-scm.org/wiki/PublishingRepositories
# Path to repo or hgweb config to serve (see 'hg help hgweb')
config = b"/path/to/repo/or/config"
# Uncomment and adjust if Mercurial is not installed system-wide
# (consult "installed modules" path from 'hg debuginstall'):
# import sys; sys.path.insert(0, "/path/to/python/lib")
from mercurial import demandimport
demandimport.enable()
from mercurial.hgweb import hgweb, wsgicgi
application = hgweb(config)
wsgicgi.launch(application)