Add migration for eo:epsg to proj:epsg

[duckontheweb]

Related Issue(s):

• Ensure migration happens correctly with SAR extension #262

Description:

Adds migration for eo:epsg to proj:epsg for pre-0.9 catalogs.

PR Checklist:

• Code is formatted (run pre-commit run --all-files)
• Tests pass (run scripts/test)
• Documentation has been updated to reflect changes, if applicable
• This PR maintains or improves overall codebase code coverage.
• Changes are added to the CHANGELOG. See the docs for information about adding to the changelog.

[codecov-commenter]

Codecov Report

Merging #557 (097f4b5) into main (660fd9a) will decrease coverage by 0.01%.
The diff coverage is 86.95%.

@@            Coverage Diff             @@
##             main     #557      +/-   ##
==========================================
- Coverage   94.50%   94.48%   -0.02%     
==========================================
  Files          71       71              
  Lines       10703    10725      +22     
  Branches     1095     1098       +3     
==========================================
+ Hits        10115    10134      +19     
- Misses        418      419       +1     
- Partials      170      172       +2     

Impacted Files	Coverage Δ
pystac/extensions/eo.py	93.30% <70.00%> (-1.12%)	⬇️
tests/extensions/test_eo.py	100.00% <100.00%> (ø)

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[lossyrob]

Was surprised to see this not accounted for...

+1 besides including a test to show it works - there's likely already a migrated example in the 0.9 example test files

[duckontheweb]

+1 besides including a test to show it works

Added in ea2ef92