Auto-sync FTR Chrome from Kibana ChromeDriver

[gurevichdmitry]

Summary of your changes

Nightly Sanity UI tests fail when Kibana's chromedriver major drifts from the hardcoded Chrome pin in the FTR action (e.g. driver 151 vs Chrome 149).

Instead of repeatedly bumping a pin, resolve the Chrome major at runtime from the checked-out Kibana devDependencies.chromedriver (same source Kibana Renovate updates), then pass it to browser-actions/setup-chrome.

Failing run that motivated this: https://github.com/elastic/cloudbeat/actions/runs/31291013098/job/93188307309

 warn SessionNotCreatedError: session not created: This version of ChromeDriver only supports Chrome version 151
      Current browser version is 149.0.7827.155 ...

Also removes the need for follow-up pin PRs like #6253 whenever Kibana bumps chromedriver.

Test plan

• Resolve step logs Resolved Chrome <major> from Kibana chromedriver@...
• Setup Chrome installs that major (currently 151 from chromedriver@151.0.3)
• Run UI Sanity checks (Kibana) gets past browser session creation (no SessionNotCreatedError)

[mergify]

This pull request does not have a backport label. Could you fix it @gurevichdmitry? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v./d./d./d is the label to automatically backport to the 8./d branch. /d is the digit
• backport-active-all is the label that automatically backports to all active branches.
• backport-active-8 is the label that automatically backports to all active minor branches for the 8 major.
• backport-active-9 is the label that automatically backports to all active minor branches for the 9 major.