Prepare for the otel v1.15.0-rc.1 release

[MrAlias]

Use otel global instead of otel/metric/global

[codecov]

Codecov Report

Merging #3518 (8c3b354) into main (3ffe346) will increase coverage by 2.9%.
The diff coverage is 50.0%.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #3518     +/-   ##
=======================================
+ Coverage   69.9%   72.9%   +2.9%     
=======================================
  Files        147     149      +2     
  Lines       6934    6980     +46     
=======================================
+ Hits        4851    5092    +241     
+ Misses      1959    1751    -208     
- Partials     124     137     +13     

Impacted Files	Coverage Δ
instrumentation/host/host.go	0.0% <0.0%> (ø)
instrumentation/runtime/runtime.go	0.0% <0.0%> (ø)
...ation/github.com/astaxie/beego/otelbeego/config.go	100.0% <100.0%> (ø)
...ntation/github.com/gocql/gocql/otelgocql/config.go	67.3% <100.0%> (+67.3%)	⬆️
...entation/google.golang.org/grpc/otelgrpc/config.go	65.1% <100.0%> (ø)
instrumentation/net/http/otelhttp/config.go	82.8% <100.0%> (ø)
.../github.com/gocql/gocql/otelgocql/internal/cass.go	95.1% <0.0%> (ø)
...n/github.com/gocql/gocql/otelgocql/test/version.go	0.0% <0.0%> (ø)
...ion/github.com/gocql/gocql/otelgocql/instrument.go	62.5% <0.0%> (+62.5%)	⬆️
... and 3 more

[MrAlias]

Merging as this blocks the release.