Functionality moved from internal/attribute to attribute (#6580)

Resolve #6525

## Description

This pull request addresses the issue of moving internal functionality
from the `internal/attribute` package to the `attribute `package within
the open-telemetry/opentelemetry-go repository. The goal is to ensure
that none of this functionality is added to the public API of the
attribute or any other public package while improving the naming,
layout, and following Go idioms.

## Changes made

1. Moved Functions to `attribute/internal`

- Created a new internal package within the `attribute` package:
`attribute/internal`.
- Moved `attribute.go` and `attribute_test.go` into the
`attribute/internal`
- Moved the following functions from `internal/attribute` to
`attribute/internal`

2 . Changes in .golangci.yml

- Removed line 67 and 68 from .golangci.yml

---------

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

.golangci.yml

@@ -64,8 +64,6 @@ linters:
           deny:
             - pkg: go.opentelemetry.io/otel/internal$
               desc: Do not use cross-module internal packages.
-            - pkg: go.opentelemetry.io/otel/internal/attribute
-              desc: Do not use cross-module internal packages.
             - pkg: go.opentelemetry.io/otel/internal/internaltest
               desc: Do not use cross-module internal packages.
             - pkg: go.opentelemetry.io/otel/internal/matchers

attribute/internal/attribute.go

@@ -5,7 +5,7 @@
 Package attribute provide several helper functions for some commonly used
 logic of processing attributes.
 */
-package attribute // import "go.opentelemetry.io/otel/internal/attribute"
+package attribute // import "go.opentelemetry.io/otel/attribute/internal"
 
 import (
 	"reflect"

attribute/value.go

@@ -9,8 +9,8 @@ import (
 	"reflect"
 	"strconv"
 
+	attribute "go.opentelemetry.io/otel/attribute/internal"
 	"go.opentelemetry.io/otel/internal"
-	"go.opentelemetry.io/otel/internal/attribute"
 )
 
 //go:generate stringer -type=Type