DuplicateOptionError when there is { in entry_points.txt file

I'm trying to build application with dependencies on taurus https://gitlab.com/taurus-org/taurus but it returns error.

It seems that configparser has problem with reading parameter starting with `{`

entry_points.txt file:
```ini
[console_scripts]
taurus = taurus.cli:main

[taurus.cli.subcommands]
check-deps = taurus._taurushelper:check_dependencies_cmd
config = taurus.qt.qtgui.panel.taurusconfigeditor:config_cmd
demo = taurus.qt.qtgui.panel.taurusdemo:demo_cmd
designer = taurus.qt.qtdesigner.taurusdesigner:designer_cmd
device = taurus.qt.qtgui.panel.taurusdevicepanel:device_cmd
form = taurus.qt.qtgui.panel.taurusform:form_cmd
gui = taurus.qt.qtgui.taurusgui.taurusgui:gui_cmd
guiqwt = taurus.qt.qtgui.extra_guiqwt.cli:guiqwt
icons = taurus.qt.qtgui.icon.catalog:icons_cmd
image = taurus.cli.alt:image_cmd
logmon = taurus.core.util.remotelogmonitor:logmon_cmd
newgui = taurus.qt.qtgui.taurusgui.taurusgui:newgui_cmd
panel = taurus.qt.qtgui.panel.taurusdevicepanel:panel_cmd
plot = taurus.cli.alt:plot_cmd
qlogmon = taurus.qt.qtgui.table.qlogtable:qlogmon_cmd
trend = taurus.cli.alt:trend_cmd
trend2d = taurus.cli.alt:trend2d_cmd

[taurus.image.alts]
guiqwt = taurus.qt.qtgui.extra_guiqwt:TaurusImageDialog

[taurus.model_selector.items]
Tango = taurus.qt.qtgui.panel.taurusmodelchooser:TangoModelSelectorItem

[taurus.qt.formatters]
tango = taurus.core.tango.util:tangoFormatter
taurus = taurus.qt.qtgui.base:defaultFormatter
{:.5f} = taurus.qt.qtgui.base:floatFormatter
{:2.3e} = taurus.qt.qtgui.base:expFormatter

[taurus.trend2d.alts]
guiqwt = taurus.qt.qtgui.extra_guiqwt:TaurusTrend2DDialog

```

error output
```
$ shiv -c myapp -o myapp . taurus
Collecting taurus
Using cached taurus-5.1.8-py3-none-any.whl (17.8 MB)
Collecting packaging
Using cached packaging-24.0-py3-none-any.whl (53 kB)
Collecting click
Using cached click-8.1.7-py3-none-any.whl (97 kB)
Collecting numpy>=1.1
Using cached numpy-1.26.4-cp39-cp39-manylinux_2_17_x86_64.manylinux2014_x86_64.whl (18.2 MB)
Collecting pint>=0.8
Using cached Pint-0.23-py3-none-any.whl (305 kB)
Collecting typing-extensions
Using cached typing_extensions-4.11.0-py3-none-any.whl (34 kB)
Installing collected packages: typing-extensions, pint, packaging, numpy, click, taurus
WARNING: Value for scheme.platlib does not match. Please report this to
distutils: /tmp/pip-target-5pu2o4pv/lib64/python
sysconfig: /tmp/pip-target-5pu2o4pv/lib/python
WARNING: Additional context:
user = False
home = '/tmp/pip-target-5pu2o4pv'
root = None
prefix = None
Successfully installed click-8.1.7 numpy-1.26.4 packaging-24.0 pint-0.23 taurus-5.1.8 typing-extensions-4.11.0
Traceback (most recent call last):
File "/home/michal.falowski/.local/bin/shiv", line 8, in
sys.exit(main())
File "/home/michal.falowski/.local/lib/python3.9/site-packages/click/core.py", line 1157, in __call__
return self.main(*args, **kwargs)
File "/home/michal.falowski/.local/lib/python3.9/site-packages/click/core.py", line 1078, in main
rv = self.invoke(ctx)
File "/home/michal.falowski/.local/lib/python3.9/site-packages/click/core.py", line 1434, in invoke
return ctx.invoke(self.callback, **ctx.params)
File "/home/michal.falowski/.local/lib/python3.9/site-packages/click/core.py", line 783, in invoke
return __callback(*args, **kwargs)
File "/home/michal.falowski/.local/lib/python3.9/site-packages/shiv/cli.py", line 236, in main
entry_point = find_entry_point(sources, console_script)
File "/home/michal.falowski/.local/lib/python3.9/site-packages/shiv/cli.py", line 46, in find_entry_point
config_parser.read(site_packages.rglob("entry_points.txt"))
File "/usr/lib64/python3.9/configparser.py", line 697, in read
self._read(fp, filename)
File "/usr/lib64/python3.9/configparser.py", line 1096, in _read
raise DuplicateOptionError(sectname, optname,
configparser.DuplicateOptionError: While reading from PosixPath('/tmp/tmpc2vzdrt4/taurus-5.1.8.dist-info/entry_points.txt') [line 33]: option '{' in section 'taurus.qt.formatters' already exists
```

Start in shiv/cli.py at find_entry_point, where config_parser.read loads entry_points.txt files. Reproduce the failure with the Taurus entry_points.txt content shown in the issue, then verify that duplicate formatter keys no longer raise DuplicateOptionError and the taurus console script can be found.

Written by the indexing model from the issue text.