feat: revert telemetry server changes

[skosito]

Description

Revert handlers in ts on port 8123. It was replaced by metrics in this PR: #1885
In this PR it is reverted, but metrics are still updated. Also changed last scanned block number to have chainName as label same as metrics.

Closes: #2324

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Include instructions and any relevant details so others can reproduce.

• Tested CCTX in localnet
• Tested in development environment
• Go unit tests
• Go integration tests
• Tested via GitHub Actions

Checklist:

• I have added unit tests that prove my fix feature works

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 72 lines in your changes missing coverage. Please review.

Project coverage is 68.06%. Comparing base (3f02526) to head (7d0ff3d).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2325      +/-   ##
===========================================
- Coverage    68.30%   68.06%   -0.24%     
===========================================
  Files          299      299              
  Lines        18905    18971      +66     
===========================================
  Hits         12913    12913              
- Misses        5355     5421      +66     
  Partials       637      637              

Files	Coverage Δ
zetaclient/chains/evm/observer/observer.go	32.04% <0.00%> (ø)
zetaclient/orchestrator/orchestrator.go	25.40% <0.00%> (ø)
zetaclient/chains/bitcoin/observer/observer.go	14.31% <0.00%> (ø)
zetaclient/metrics/telemetry.go	0.00% <0.00%> (ø)

[github-actions]

!!!WARNING!!!
nosec detected in the following files: zetaclient/chains/bitcoin/observer/observer.go

Be very careful about using #nosec in code. It can be a quick way to suppress security warnings and move forward with development, it should be employed with caution. Suppressing warnings with #nosec can hide potentially serious vulnerabilities. Only use #nosec when you're absolutely certain that the security issue is either a false positive or has been mitigated in another way.

Only suppress a single rule (or a specific set of rules) within a section of code, while continuing to scan for other problems. To do this, you can list the rule(s) to be suppressed within the #nosec annotation, e.g: /* #nosec G401 */ or //#nosec G201 G202 G203
Broad #nosec annotations should be avoided, as they can hide other vulnerabilities. The CI will block you from merging this PR until you remove #nosec annotations that do not target specific rules.

Pay extra attention to the way #nosec is being used in the files listed above.

[brewmaster012]

has this been tested in localnet?

[skosito]

has this been tested in localnet?

yes i tested locally that following endpoints on 8123 work, and values are present in metrics on 8886 as well:

/version
/lastscannedblock
/laststarttimestamp
/lastcoreblock
/status

[kingpinXD]

LGTM .
Minor comments

[lumtis]

LGTM