Url decode link column display values if regex is used (#8258)

## Describe your changes

This PR decodes the extracted display values. This is needed since its
extracted from an URL, which often requires URL encoding certain chars.

This also includes a small slightly unrelated one-liner addition to
resolve this issue with the link column:
#7064 (Closes #7064)

## Testing Plan

- Added unit test

---

**Contribution License Agreement**

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project are made under the Apache 2.0 license.

frontend/lib/src/components/widgets/DataFrame/columns/LinkColumn.test.ts

@@ -201,6 +201,22 @@ describe("LinkColumn", () => {
     expect(cell.displayData).toBe("roadmap")
   })
 
+  it("sets displayed value as the applied regex to the href when displayText is a regex with URL encoding", () => {
+    const mockColumn = LinkColumn({
+      ...MOCK_LINK_COLUMN_PROPS,
+      columnTypeOptions: {
+        display_text: "https://streamlit\\.app\\?app=(.*)",
+      },
+    })
+
+    const cell = mockColumn.getCell(
+      "https://streamlit.app?app=foo%20app%20%25",
+      true
+    ) as UriCell
+
+    expect(cell.displayData).toBe("foo app %")
+  })
+
   it("sets displayed value as the href, when displayText is a regex but there is no match", () => {
     const mockColumn = LinkColumn({
       ...MOCK_LINK_COLUMN_PROPS,

frontend/lib/src/components/widgets/DataFrame/columns/LinkColumn.ts

@@ -160,7 +160,11 @@ function LinkColumn(props: BaseColumnProps): BaseColumn {
         displayData: displayText,
         isMissingValue: isNullOrUndefined(href),
         onClickUri: a => {
-          window.open(href, "_blank", "noopener,noreferrer")
+          window.open(
+            href.startsWith("www.") ? `https://${href}` : href,
+            "_blank",
+            "noopener,noreferrer"
+          )
           a.preventDefault()
         },
         copyData: href,

frontend/lib/src/components/widgets/DataFrame/columns/utils.ts

@@ -662,7 +662,8 @@ export function getLinkDisplayValueFromRegex(
     const patternMatch = href.match(displayTextRegex)
     if (patternMatch && patternMatch[1] !== undefined) {
       // return the first matching group
-      return patternMatch[1]
+      // Since this might be a URI encoded value, we decode it.
+      return decodeURI(patternMatch[1])
     }
 
     // if the regex doesn't find a match with the url, just use the url as display value