Add missing defusedxml

[fwfichtner]

• adds defusedxml to msi_reader extra
• adds new extra avhrr_l1b_eps because it was also missing defusedxml

Feel free to cherry-pick if you don't like the new reader.

• [x] Closes #2759
• [ ] Tests added

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.92%. Comparing base (85d9117) to head (45f918e). Report is 34 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2761 +/- ## ========================================== - Coverage 95.94% 95.92% -0.03% ========================================== Files 375 377 +2 Lines 53293 53468 +175 ========================================== + Hits 51130 51287 +157 - Misses 2163 2181 +18 ``` | [Flag](https://app.codecov.io/gh/pytroll/satpy/pull/2761/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytroll) | Coverage Δ | | |---|---|---| | [behaviourtests](https://app.codecov.io/gh/pytroll/satpy/pull/2761/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytroll) | `4.11% <ø> (-0.02%)` | :arrow_down: | | [unittests](https://app.codecov.io/gh/pytroll/satpy/pull/2761/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytroll) | `96.01% <ø> (-0.03%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytroll#carryforward-flags-in-the-pull-request-comment) to find out more.

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[coveralls]

Pull Request Test Coverage Report for Build 8278663645

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 95.999%

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Totals
Change from base Build 8205996229:	0.0%
Covered Lines:	51159
Relevant Lines:	53291

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💛 - Coveralls