Fix \?, \+ and \| to be treated as ERE in BRE mode

[LoukasPap]

Fixes #288.

It also passes a test from the GNU testsuite comparison.

The brace quantifiers { and } are not included because they are already solved in PR #328.

[github-actions]

GNU sed testsuite comparison:

Test results comparison:
  Current:   TOTAL: 65 / PASSED: 8 / FAILED: 47 / SKIPPED: 10
  Reference: TOTAL: 65 / PASSED: 7 / FAILED: 48 / SKIPPED: 10

Changes from main branch:
  TOTAL: +0
  PASSED: +1
  FAILED: -1

Test improvements (1):
  + posix-mode-ERE

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.29%. Comparing base (d7a713e) to head (2520eb6).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #381      +/-   ##
==========================================
+ Coverage   82.25%   82.29%   +0.03%     
==========================================
  Files          13       13              
  Lines        5522     5534      +12     
  Branches      310      310              
==========================================
+ Hits         4542     4554      +12     
  Misses        977      977              
  Partials        3        3              

Flag	Coverage Δ
macos_latest	82.97% <100.00%> (+0.03%)	⬆️
ubuntu_latest	83.08% <100.00%> (+0.03%)	⬆️
windows_latest	0.00% <0.00%> (ø)

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[sylvestre]

please add an integration tests in tests/by-util/test_sed.rs
high level test is also important, thanks

[github-actions]

GNU sed testsuite comparison:

Test results comparison:
  Current:   TOTAL: 65 / PASSED: 8 / FAILED: 47 / SKIPPED: 10
  Reference: TOTAL: 65 / PASSED: 7 / FAILED: 48 / SKIPPED: 10

Changes from main branch:
  TOTAL: +0
  PASSED: +1
  FAILED: -1

Test improvements (1):
  + posix-mode-ERE

[LoukasPap]

Added 3 tests.