Signed-off-by: Ole Herman Schumacher Elgesem <ole@northern.tech>

This test validates that select_region can converge across multiple
edit_line passes when the region is created in an earlier pass.

The test creates a file with a [section] header in the first promise,
then uses select_region to insert content within that section in the
second promise. This demonstrates that select_region failures are
retried across multiple passes until they succeed.

Ticket: CFE-3866
Changelog: None

Modified edit_line operations to allow select_region to succeed across
multiple convergence passes. Previously, if a promise inserted a section
header in pass 1, promises using select_region for that section would
fail with INTERRUPTED in the same run, preventing convergence.

Changes:
- Added EDIT_CONTEXT_IS_FINAL_PASS macro to files_edit.h for checking
  if we're on the final convergence pass
- Extracted HandleSelectRegionFailure() to centralize error handling
  for SelectRegion failures across VerifyLineDeletions, VerifyColumnEdits,
  VerifyPatterns, and VerifyLineInsertions
- On non-final passes: log verbose message and return NOOP to allow retry
- On final pass: report error with detailed context
- Log messages now show remaining passes (e.g., "pass 1/3, 2 more passes to try")

This eliminates the need for workarounds in set_variable_values_ini()
and similar functions that create sections and immediately edit them.

Ticket: CFE-3866
Changelog: Title