test: Regolden escape slash SPEF

Use the existing escape_slash.spefok and escape_slash_hier.spefok files for exact SPEF matching instead of adding separate reduced golden names.

This keeps the regression checking structure unchanged while preserving the reduced fixtures and read_verilog coverage.

Tested: bazel test //src/dbSta/test:escape_slash-tcl_test //src/dbSta/test:escape_slash_hier-tcl_test

Co-authored-by: OmX <omx@oh-my-codex.dev>
Signed-off-by: Jaehyun Kim <jhkim@precisioninno.com>

Author: jhkim-pii