fix(select): popover can be scrolled (#28965)

Issue number: resolves #28963 --------- <!-- Please do not submit updates to dependencies unless it fixes an issue. --> <!-- Please try to limit your pull request to one type (bugfix, feature, etc). Submit multiple pull requests if needed. --> ## What is the current behavior? <!-- Please describe the current behavior that you are modifying. --> In #28861 I fixed an issue that caused the wrong content inside of a popover to be scrollable. This CSS should have been applied, but it broke back when popover was converted to the Shadow DOM. Fixing this issue revealed a misconfiguration with the select-popover that caused the select-popover to no longer be scrollable. ## What is the new behavior? <!-- Please describe the behavior or changes that are being added by this PR. --> - Content inside of `ion-select-popover` can now be scrolled Note that I am considering this a bug fix instead of a regression. While scrolling used to work in select-popover, it only worked by chance. The `.popover-viewport` styles should have always applied to the select-popover, thus requiring the use of `overflow-y: auto` in select-popover. ## Does this introduce a breaking change? - [ ] Yes - [x] No <!-- If this introduces a breaking change: 1. Describe the impact and migration path for existing applications below. 2. Update the BREAKING.md file with the breaking change. 3. Add "BREAKING CHANGE: [...]" to the commit description when merging. See https://github.com/ionic-team/ionic-framework/blob/main/.github/CONTRIBUTING.md#footer for more information. --> ## Other information <!-- Any other information that is important to this PR such as screenshots of how the component looks before and after the change. --> Dev build: `7.7.1-dev.11706893059.1bef4b38`

Author: liamdebeasi

core/src/components/select-popover/select-popover.scss

@@ -8,3 +8,14 @@ ion-list-header,
 ion-label {
  @include margin(0);
 }
+
+
+/**
+ * The main content inside of a popover has overflow: hidden
+ * so that a descendant ion-content can be scrolled.
+ * However, select-popover does not use ion-content so we need
+ * to explicitly make this container scrollable.
+ */
+:host {
+ overflow-y: auto;
+}