Support displaying indexed filenames for large files

What does this MR do?

Related to gitlab-elasticsearch-indexer#76 (closed)

• Update to the latest release tag for the gitlab-elasticsearch-indexer
• The newest version supports indexing file name only for files where the content is over the Maximum Indexed File Size
• Display a message to the user if the file content is empty when searching. Note: The indexed data cannot tell us if the file is empty or too large so the messaging has to be more general
• Update Admin Settings UI
• Update documentation

How to test

Note: I had some trouble getting my gdk to switch over to using the new indexer. What you can do is:

• clone the indexer (https://gitlab.com/gitlab-org/gitlab-elasticsearch-indexer)
• follow instructions on how to build a local version
• copy the newly built version to [GDK_DIRECTORY]/gitlab-elasticsearch-indexer/bin
• verify you have the v2.13.0 version: [GDK_DIRECTORY]/gitlab-elasticsearch-indexer/bin/./gitlab-elasticsearch-indexer --version

in GDK

• Get your gdk setup to work with Elasticsearch and create your index
• Upload a large file to any repository (needs to be over 1024 KiB or whatever the Maximum indexed file size is from the Advanced Search Admin Settings)
• Search for the file by name or search for everything by using *
• verify the new text is used in place of an empty code block

Screenshots or Screencasts (strongly suggested)

Before

After

Shows both an empty file and a file that is too large to index

Admin UI text update

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Security

Does this MR contain changes to processing or storing of credentials or tokens, authorization and authentication methods or other items described in the security review guidelines? If not, then delete this Security section.

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team