[receiver/tcpcheck] unexport TCPConnectionState (#40271)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description
Unexport TCPConnectionState.

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: atoulme

.chloggen/unexport_tcpconnectionstate.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: breaking
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: tcpcheckreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Unexport TCPConnectionState
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [40271]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [api]

receiver/tcpcheckreceiver/scraper.go

@@ -22,23 +22,23 @@ type scraper struct {
 	cfg                *Config
 	settings           component.TelemetrySettings
 	mb                 *metadata.MetricsBuilder
-	getConnectionState func(tcpConfig *confignet.TCPAddrConfig) (TCPConnectionState, error)
+	getConnectionState func(tcpConfig *confignet.TCPAddrConfig) (tcpConnectionState, error)
 	errorCounts        map[string]int64
 }
 
-type TCPConnectionState struct {
+type tcpConnectionState struct {
 	LocalAddr  string // Local address of the connection
 	RemoteAddr string // Remote address of the connection
 	Network    string // Network type (e.g., "tcp")
 }
 
-func getConnectionState(tcpConfig *confignet.TCPAddrConfig) (TCPConnectionState, error) {
+func getConnectionState(tcpConfig *confignet.TCPAddrConfig) (tcpConnectionState, error) {
 	conn, err := tcpConfig.Dial(context.Background())
 	if err != nil {
-		return TCPConnectionState{}, err
+		return tcpConnectionState{}, err
 	}
 	defer conn.Close()
-	state := TCPConnectionState{
+	state := tcpConnectionState{
 		LocalAddr:  conn.LocalAddr().String(),
 		RemoteAddr: conn.RemoteAddr().String(),
 		Network:    conn.LocalAddr().Network(),