PMM-14977 improve home dashboard

[igroene]

Changes made:

• Made the values in the Monitored DB Services panel clickable by technology.
• Added direct links from each technology count to its corresponding overview dashboard:
  • MySQL -> MySQL Instances Overview
  • MongoDB -> MongoDB Instances Overview
  • PostgreSQL -> PostgreSQL Instances Overview
  • ProxySQL -> ProxySQL Instance Summary
  • Valkey -> Valkey Overview
• Added missing tooltips/descriptions to Overview panels that previously had no tooltip.
• Updated the tooltips for Monitored DB Services and Monitored DB Instances to clearly explain the difference between the two panels:
  • Monitored DB Services counts monitored endpoints/scrape targets per technology
  • Monitored DB Instances counts distinct logical database services per technology, deduplicating multiple endpoints belonging to the same service
    Outcome:
• Users can now click directly from the service counts on the Home dashboard to the relevant technology dashboard.
• The Overview section now has more complete and clearer tooltip guidance, especially for the two similarly named database count panels.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 47.43%. Comparing base (38c9b56) to head (217d259).

Additional details and impacted files

@@            Coverage Diff             @@
##               v3    #5221      +/-   ##
==========================================
- Coverage   47.79%   47.43%   -0.37%     
==========================================
  Files         410      540     +130     
  Lines       41981    44325    +2344     
  Branches        0      591     +591     
==========================================
+ Hits        20066    21026     +960     
- Misses      19940    21260    +1320     
- Partials     1975     2039      +64     

Flag	Coverage Δ
admin	35.80% <ø> (ø)
agent	53.24% <ø> (-0.10%)	⬇️
unittests	41.38% <ø> (?)

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