[Fleet] allow alpha, beta, rc suffixes in agent versions (elastic#211787

)

## Summary

Closes elastic#211777

Add agent flyout should show `9.0.0-beta1` now:
<img width="2540" alt="image"
src="https://github.com/user-attachments/assets/86259eea-5858-4d06-8989-8fadb3a57f96"
/>

When `9.0.0` comes out, that should show up as latest. For example,
`8.0.0` versions come back in this order:
<img width="462" alt="image"
src="https://github.com/user-attachments/assets/c5204806-3cf7-4c65-bb60-21d176f24f17"
/>



### Checklist

- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios

x-pack/platform/plugins/shared/fleet/server/services/agents/versions.test.ts

@@ -229,14 +229,26 @@ describe('getAvailableVersions', () => {
       text: jest.fn().mockResolvedValue(
         JSON.stringify([
           [
+            {
+              title: 'Elastic Agent 9.0.0',
+              version_number: '9.0.0-rc1',
+            },
             {
               title: 'Elastic Agent 8.0.0',
-              version_number: '8.0.0-rc1',
+              version_number: '8.0.0-rc2',
             },
             {
               title: 'Elastic Agent 8.0.0',
               version_number: '8.0.0-beta1',
             },
+            {
+              title: 'Elastic Agent 8.0.0',
+              version_number: '8.0.0-alpha1',
+            },
+            {
+              title: 'Elastic Agent 8.0.0',
+              version_number: '8.0.0-unkown',
+            },
           ],
         ])
       ),

x-pack/platform/plugins/shared/fleet/server/services/agents/versions.ts

@@ -15,7 +15,7 @@ import semverGte from 'semver/functions/gte';
 import semverGt from 'semver/functions/gt';
 import semverRcompare from 'semver/functions/rcompare';
 import semverLt from 'semver/functions/lt';
-import semverCoerce from 'semver/functions/coerce';
+import semverParse from 'semver/functions/parse';
 
 import { REPO_ROOT } from '@kbn/repo-info';
 
@@ -114,8 +114,18 @@ export const getAvailableVersions = async ({
   // only want support versions in the final result. We'll also sort by newest version first.
   availableVersions = uniq(
     [...availableVersions, ...apiVersions]
-      .map((item: any) => (item.includes('+build') ? item : semverCoerce(item)?.version || ''))
-      .filter((v: any) => semverGte(v, MINIMUM_SUPPORTED_VERSION))
+      .filter((v: any) => {
+        const parsedVersion = semverParse(v);
+        if (
+          parsedVersion?.prerelease?.length &&
+          !parsedVersion.prerelease.some(
+            (prerelease) => typeof prerelease === 'string' && prerelease.includes('+build')
+          )
+        ) {
+          return false;
+        }
+        return semverGte(v, MINIMUM_SUPPORTED_VERSION);
+      })
       .sort((a: any, b: any) => (semverGt(a, b) ? -1 : 1))
   );