fixed file list pagination not working when filtering file extensions

[andyevers]

Closes # 3413

PR Type

• Bugfix

Description of the changes

• Fixed broken pagination when filtering by extension. This was caused by this._preloadedFiles not being updated after fetching data in mgt-file-list.ts.
• Additionally, files will now be fetched using the maximum pagination size because the pagination is done on the client side here. after everything is fetched, pagination will use the user-defined page size normally.

PR checklist

• Project builds (yarn build) and changes have been tested in at least two supported browsers (Edge + non-Chromium based browser)
• All public APIs (classes, methods, etc) have been documented following the jsdoc syntax
• Stories have been added and existing stories have been tested
• Added appropriate documentation. Docs PR:
• License header has been added to all new source files (yarn setLicense)
• Contains NO breaking changes

[microsoft-github-policy-service]

Thank you for creating a Pull Request @andyevers.

This is a checklist for the PR reviewer(s) to complete before approving and merging this PR:

• I have verified a documentation PR has been linked and is approved (or not applicable)
• I have ran this PR locally and have tested the fix/feature
• I have verified that stories have been added to storybook (or not applicable)
• I have tested existing stories in storybook to verify no regression has occured
• I have tested the solution in at least two browsers (Edge + 1 non-Chromium based browser)