Properly escape special characters in comments

[angelamayxie]

Mostly fixes dolthub/dolt#8509 (does not handle Control+Z)

[jycor]

LGTM!

Add some ALTER TABLE tests in gms/enginetest/queries/alter_table_queries.go
Something like

	{
		Name: "alter table comments are also escaped",
		SetUpScript: []string{
			"create table t (i int);",
			`alter table t modify column i int comment ...`,
			`alter table t add column j int comment ...`,
		},
		Assertions: []ScriptTestAssertion{
			{
				Query: "show create table t",
				Expected: []sql.Row{
					{...},
				},
			},
		},
	},