### Motivation
It's very annoying to search env variable exactly by lprefix. The better
is to search by substring and sort results by the position of substring
and then alphabetically.
Closes#5386
### Before
```xsh
$TRA<Tab>
# nothing
```
### After
```xsh
$TRA<Tab>
# 'XONSH_TRACE_COMPLETIONS',
# 'XONSH_TRACE_SUBPROC',
# 'XONSH_TRACE_SUBPROC_FUNC',
# 'XONSH_TRACEBACK_LOGFILE',
# 'XONSH_SHOW_TRACEBACK',
# 'VC_GIT_INCLUDE_UNTRACKED'
```
## For community
⬇️ **Please click the 👍 reaction instead of leaving a `+1` or 👍
comment**
---------
Co-authored-by: a <1@1.1>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
* todo
* test: remove usage of DummyEnv and setting .env attribute on xession fixture
one step closer to making too much of tweaking to xession during tests
* test: fix tests vox and gitstatus-prompt
* docs: update test-fixture usage
* fix: import flake8 error
* test: remove direct access to XSH in tests
* test: remove usage of XSH in test files
* todo
* test: use tmp-dir to create stubs
* refactor: use fixture factory to mock out XonshSession
* refactor: remove direct access of XSH from functions
* refactor: remove direct access of XSH from functions
* fix: qa checks
* refactor: rename variables to match their values
* test: update failing tests because it had no PATH set previously
* fix: remove builtins usage from pyghooks.py
* style:
* refactor: update tests to use fixtures
* fix: env varialbe is setup per function
some tests accidentally update the env variables and that is leaking
into next tests
* fix: failing vox tests
* test: set commands_cache per test
* test: fix failing tests
* fix: failing tests on linux
ptk-highlight
* fix: failing tests on Windows
cwd-prompt
* test: copy env as to not affect original object
* fix: lazily evaluate cmds-cache in pyghooks
* test: fix failing tests
* fix: qa errors import
* test: set commands-cache per test
while caching path results
* test: speedup test_thread_local_swap
* fix: failing tests on windows
* refactor: Execer doesn't control session
* refactor: XSH.unload will take care of reversing builtins attrs set
* test: use env.update over monkeypatch
* Revert "test: use env.update over monkeypatch"
This reverts commit 010a5022247a098f1741966b8af1bf758663480e.
* refactor: remove usage of global variables in abbrevs.py
* chore: add flake8-mutable to prevent mutable defaults
* fix: abbrevs expand test
* refactor: add xonsh session singleton
* refactor: fix circular errors when using xonshSession as singleton
* refactor: remove black magicked builtin attributes
* style: black format tests as well
* refactor: update tests to use xonsh-session singleton
* refactor: update abbrevs to not use builtins
* test: remove DummyCommandsCache and patch orig class
* fix: failing test_command_completers
* test: use monkeypatch to update xession fixture
* fix: failing test_pipelines
* fix: failing test_main
* chore: run test suit as single invocation
* test: fix tests/test_xonsh.xsh
* refactor: remove builtins from docs/conf.py
* fix: mypy error in jobs
* fix: test error from test_main
* test: close xession error in test_command_completers
* chore: use pytest-cov for reporting coverage
this will include subprocess calls, and will increase coverage
* style:
