refactor(instr-fastify): use exported strings for attributes

[david-luna]

Which problem is this PR solving?

• Updates Update usage of semantic conventions to new exported strings #2025

Short description of the changes

• Update @opentelemetry/semantic-conventions to ^1.22
• Replace SemanticAttributes.HTTP_ROUTE with exported string SEMATTRS_HTTP_ROUTE
• Update README with new semantic convention package version and key

[codecov]

Codecov Report

Merging #2078 (853688e) into main (dfb2dff) will decrease coverage by 0.69%.
Report is 33 commits behind head on main.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2078      +/-   ##
==========================================
- Coverage   90.97%   90.29%   -0.69%     
==========================================
  Files         146      139       -7     
  Lines        7492     6891     -601     
  Branches     1502     1379     -123     
==========================================
- Hits         6816     6222     -594     
+ Misses        676      669       -7     

Files	Coverage Δ
...try-instrumentation-fastify/src/instrumentation.ts	95.48% <100.00%> (ø)

... and 14 files with indirect coverage changes

[david-luna]

Note for reviewer: this import was unused