[dbnode] Peers bootstrapper progress gauges

[soundvibe]

What this PR does / why we need it:

This PR adds new gauges to track peers bootstrapper progress.

Special notes for your reviewer:

Does this PR introduce a user-facing and/or backwards incompatible change?:

Does this PR require updating code package or user-facing documentation?:

[codecov]

Codecov Report

❌ Patch coverage is 81.81818% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 66.4%. Comparing base (4f035bd) to head (c6fa769).
⚠️ Report is 639 commits behind head on master.

❗ There is a different number of reports uploaded between BASE (4f035bd) and HEAD (c6fa769). Click for more details.

HEAD has 79 uploads less than BASE

Flag	BASE (4f035bd)	HEAD (c6fa769)
collector	21	10
aggregator	21	10
m3em	20	10
cluster	20	10
msg	8	4
dbnode	18	9
query	12	5
m3ninx	12	5
x	12	5
metrics	7	4

Additional details and impacted files

@@            Coverage Diff            @@
##           master    #3434     +/-   ##
=========================================
- Coverage    72.6%    66.4%   -6.3%     
=========================================
  Files        1100     1097      -3     
  Lines      103600   102609    -991     
=========================================
- Hits        75297    68163   -7134     
- Misses      23199    29697   +6498     
+ Partials     5104     4749    -355     

Flag	Coverage Δ
aggregator	75.5% <ø> (-1.4%)	⬇️
cluster	77.5% <ø> (-7.4%)	⬇️
collector	65.3% <ø> (-19.0%)	⬇️
dbnode	77.9% <81.8%> (-1.5%)	⬇️
m3em	58.1% <ø> (-16.3%)	⬇️
m3ninx	64.9% <ø> (-8.7%)	⬇️
metrics	19.7% <ø> (ø)
msg	74.7% <ø> (+<0.1%)	⬆️
query	50.1% <ø> (-16.9%)	⬇️
x	73.0% <ø> (-7.3%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

---

Continue to review full report in Codecov by Harness.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 4f035bd...c6fa769. Read the comment docs.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

---

Linas Naginionis seems not to be a GitHub user. You need a GitHub account to be able to sign the CLA. If you have already a GitHub account, please add the email address used for this commit to your account.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}