feat: add option to separate configs by tags on export

[wakonig]

Description

bec.config.save_current_session now supports the export by tags.

Additional Comments

Once merged, we can add it also to the DeviceManagerView

Definition of Done

• Documentation is up-to-date.

[Copilot]

Pull request overview

This PR enhances the device configuration export workflow by adding an option to export the current session split into multiple YAML files grouped by deviceTags, and it also refactors/extends the config helper API (set_session, add_to_session, save_session) while keeping backward-compatible aliases.

Changes:

• Added save_session(..., split_by_tag=True) to write a manifest plus one YAML file per tag (and an untagged bucket).
• Introduced set_session (replacement for update_session_with_file) and added add_to_session; updated call sites/tests accordingly.
• Added unit tests covering split-by-tag export behavior and updated e2e tests to use set_session.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.

File	Description
bec_lib/tests/test_config_helper.py	Updates tests for the new API names and adds coverage for split-by-tag export output.
bec_lib/bec_lib/config_helper.py	Implements split_by_tag export, adds add_to_session, refactors session APIs, and introduces helper functions for split output generation.
bec_ipython_client/tests/end-2-end/test_scans_lib_e2e.py	Updates e2e tests to use set_session instead of update_session_with_file.

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[codecov]

Codecov Report

❌ Patch coverage is 88.23529% with 14 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
bec_lib/bec_lib/config_helper.py	88.13%	10 Missing and 4 partials ⚠️

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