Issue #7903 : Add find and replace to the explorer content editor

[mattcasters]

Summary

• Adds Find and Find/Replace to the shared content-editor toolbar and desktop popup used by BaseTextExplorerFileType (Open as text, YAML, SQL, XML, logs, markdown).
• Generalizes FindReplaceDialog onto IFindReplaceTarget so explorer tabs reuse the same dialog as TextComposite (next/previous, wrap, case sensitive, replace one/all).
• Implements selection/caret/insert on the desktop SourceViewer, Hop Web fallback Text, and Monaco remote methods so toolbar actions work in both GUIs.
• Ctrl+F / Ctrl+H while the editor is focused open the local dialog; Hop GUI Edit → Find (Search Everywhere) is unchanged.

Fixes #7903

Test plan

• Compile ui, rcp, rap
• Unit tests: FindReplaceOperationsTest, ContentEditorActionsTest, TextFindSupportTest, GuiPluginWebCompatibilityTest
• Spotless apply on changed modules
• Open .hpl / .hwf as text: Find and Find/Replace on toolbar and popup
• Find next/previous wraps and seeds from the current selection
• Replace one / replace all marks the file dirty
• Read-only / binary open-as-text: Find enabled, Replace disabled
• YAML / SQL / XML / markdown tabs get the same buttons
• Dialog TextComposite Find / Replace still works
• Editor focused: Ctrl+F opens the local dialog; graph focused: Ctrl+F still opens Search Everywhere