The root `sentry-go` packaged uses a different context value vs `sentry-go/gin`

## Summary

The `GetHubFromContext` in the `github.com/getsentry/sentry-go` package isn't compatible with the `GetHubFromContext` from `github.com/getsentry/sentry-go/gin` since they both use a different value when putting the `Hub` into their respective contexts.

## Steps To Reproduce

```go

package main

import (
"context"
"fmt"

"github.com/getsentry/sentry-go"
sentrygin "github.com/getsentry/sentry-go/gin"
)

func check(err error) {
if err != nil {
panic(err)
}
}

func main() {
err := sentry.Init(sentrySdk.ClientOptions{
Dsn: "https://00000000000000000000000000000000@o62611.ingest.sentry.io/0000008",
Debug: true,
})
check(err)

ctx := context.Background()
ctx = sentry.SetHubOnContext(ctx)

fmt.Printf("I will be found %t", sentry.GetHubFromContext(ctx) != nil)
fmt.Printf("I not will be found %t", sentrygin.GetHubFromContext(ctx) != nil)
}
```

The value used to set the `hub` in context in gin is `"sentry"`, [here](https://github.com/getsentry/sentry-go/blob/v0.17.0/gin/sentrygin.go#L15). The value used to set `Hub` in the is `HubContextKey` [here](https://github.com/getsentry/sentry-go/blob/v0.17.0/hub.go#L15).

This is probably the case since `gin.Context` doesn't play well with the `context.Context` interface and has it's own way of setting values. The `HubContextKey` is exported from the `github.com/getsentry/sentry-go` package so it should be possible to switch it over to keep everything consistent.

The problem would be if you would have to set both for some time in case a user has hard-coded the key in their code instead of using the function. In that case, it could be a breaking change even if the value isn't exported out of the `sentry-go/gin` package.

## Expected Behavior

Expected that using the sentry package would be compatible across. This leads to the application having to know what the higher context is doing instead of letting the `context.Context` interface get passed through. I was very confused when my gin servers weren't reporting any events.

### SDK
- `sentry-go` version: `v0.17.0`
- Go version: `19`
- Using Go Modules? yes

### Sentry
- Using hosted Sentry in sentry.io? yes
- Anything particular to your environment that could be related to this issue? no