Adds code to replace plot data for modified slicers

[DrPaulSharp]

Description

In #1371, code was introduced that appended plot data to the list of 1D data. This PR takes a find and replace approach uinstead, so that the number of entries is reasonable when pressing the "send to data explorer" button.

Fixes the second part of #4003

How Has This Been Tested?

Test suite and manually examined changes to slicers.

Review Checklist:

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Documentation (check at least one)

• There is nothing that needs documenting
• Documentation changes are in this PR
• There is an issue open for the documentation (link?)

Installers

• There is a chance this will affect the installers, if so
  • Windows installer (GH artifact) has been tested (installed and worked)
  • MacOSX installer (GH artifact) has been tested (installed and worked)
  • Wheels installer (GH artifact) has been tested (installed and worked)

Licensing (untick if necessary)

• The introduced changes comply with SasView license (BSD 3-Clause)