Core,Tests: respect .NET API conventions

Suffix "Async" for methods is for methods that return
"Task<Foo>", not "Async<Foo".

For more info, see the PR for an upcoming FSharpLint
rule:
#586

Author: knocte

src/FSharpLint.Core/Application/Lint.fs

@@ -585,7 +585,7 @@ module Lint =
             LintResult.Failure (RunTimeConfigError err)
 
     /// Lints F# source code.
-    let lintSourceAsync optionalParams source =
+    let asyncLintSource optionalParams source =
         async {
             let checker = FSharpChecker.Create(keepAssemblyContents=true)
 
@@ -602,7 +602,7 @@ module Lint =
 
     /// Lints F# source code.
     let lintSource optionalParams source =
-        lintSourceAsync optionalParams source |> Async.RunSynchronously
+        asyncLintSource optionalParams source |> Async.RunSynchronously
 
     /// Lints an F# file that has already been parsed using `FSharp.Compiler.Services` in the calling application.
     let lintParsedFile (optionalParams:OptionalLintParameters) (parsedFileInfo:ParsedFileInformation) (filePath:string) =

src/FSharpLint.Core/Application/Lint.fsi

@@ -157,7 +157,7 @@ module Lint =
     val lintSource : optionalParams:OptionalLintParameters -> source:string -> LintResult
 
     /// Lints F# source code async.
-    val lintSourceAsync : optionalParams:OptionalLintParameters -> source:string -> Async<LintResult>
+    val asyncLintSource : optionalParams:OptionalLintParameters -> source:string -> Async<LintResult>
 
     /// Lints F# source code that has already been parsed using
     /// `FSharp.Compiler.Services` in the calling application.
@@ -171,4 +171,4 @@ module Lint =
 
     /// Lints an F# file that has already been parsed using
     /// `FSharp.Compiler.Services` in the calling application.
-    val lintParsedFile : optionalParams:OptionalLintParameters -> parsedFileInfo:ParsedFileInformation -> filePath:string -> LintResult
+    val lintParsedFile : optionalParams:OptionalLintParameters -> parsedFileInfo:ParsedFileInformation -> filePath:string -> LintResult

tests/FSharpLint.Core.Tests/TestUtils.fs

@@ -15,7 +15,7 @@
 
     let private performanceTestSourceFile = basePath </> "TypeChecker.fs"
 
-    let generateAstAsync source =
+    let asyncGenerateAst source =
         async {
             let checker = FSharpChecker.Create(keepAssemblyContents=true)
             let sourceText = SourceText.ofString source
@@ -30,7 +30,7 @@
         }
 
     let generateAst source =
-        generateAstAsync source |> Async.RunSynchronously
+        asyncGenerateAst source |> Async.RunSynchronously
 
     let getPerformanceTestInput =
         let memoizedResult = ref None