Fix gRPC instrumentation on recent kernels

[edeNFed]

In recent kernel versions, the eBPF verifier checks that a valid number of bytes (positive and not overflow) are being written/read from memory.
This PR adds additional bound checks so gRPC instrumentation now passes verification.

Tested on Ubuntu 20.02, x86, running in DigitalOcean.

• Closes gRPC CreateHeaderFields probe fails with permission denied #78
• Closes the otel-go-instrumentation not works as expected in ubuntu 22.04 #141

[vreynolds]

I tested this with the example in #78 and it no longer errors!

This is the gRPC client span that's generated in the collector logs. It seems to be missing trace id and span id, and has a start time a few days in the past 😕 It could be an issue with the example app I'm using, but either way I think this fix addresses the error with loading the probe and this could be a separate issue.

ScopeSpans #0
ScopeSpans SchemaURL: 
InstrumentationScope google.golang.org/grpc 
Span #0
    Trace ID       : 
    Parent ID      : 
    ID             : 
    Name           : 
    Kind           : Client
    Start time     : 2023-05-04 19:01:53.589758682 +0000 UTC
    End time       : 2023-05-08 18:12:17.335586279 +0000 UTC
    Status code    : Unset
    Status message : 
Attributes:
     -> rpc.system: Str(grpc)
     -> rpc.service: Str()
     -> net.peer.ip: Str()
     -> net.peer.name: Str()

[edeNFed]

@vreynolds thanks for trying it out! I tested it with the emojivoto application and sent the traces to Jaeger which looked good (correct spans + context propagation