[Parse] Don't propagate static spelling to AST while parsing top level decls

[rintaro]

FuncDecl of static func foo() {} in top level was accidentally isStatic().
That causes assertion failure in ASTPrinter.

This was the immediate cause of compiler_crashers/28429-swift-decl-print.swift .

[slavapestov]

Shouldn't you run resolve-crashers.py to move that crasher to compiler_crashers_fixed?

[slavapestov]

@swift-ci Please smoke test

[rintaro]

@slavapestov
This PR does not resolve the crasher, because #5099 is the root cause of that.
It seems that #5099 causes ASTVerifier error, but because of this problem, it fails to emit diagnostic message.

28429-swift-decl-print.swift output after this PR

child source range not contained within its parent: func g()
  parent range: [validation-test/compiler_crashers/28429-swift-decl-print.swift:10:1 - line:11:16] RangeText="{class
func g:protocol<"
  child range: [validation-test/compiler_crashers/28429-swift-decl-print.swift:11:1 - line:12:1] RangeText="func g:protocol<
"
0  swift           0x00000000034bc4a8 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 40
1  swift           0x00000000034bd086
2  libpthread.so.0 0x00007fc3dd475d10
3  libc.so.6       0x00007fc3dbdbd1c7 gsignal + 55
4  libc.so.6       0x00007fc3dbdbee2a abort + 362
5  swift           0x00000000010f2de4
6  swift           0x00000000010f047f
7  swift           0x00000000010ef1eb
8  swift           0x00000000010fde39
9  swift           0x00000000010ff482
10 swift           0x000000000110284c
11 swift           0x00000000010ff427
12 swift           0x00000000010fdbca
13 swift           0x00000000010fd794 swift::Decl::walk(swift::ASTWalker&) + 20
14 swift           0x0000000001152aee swift::SourceFile::walk(swift::ASTWalker&) + 174
15 swift           0x00000000010e53e5 swift::verify(swift::SourceFile&) + 53
16 swift           0x0000000000ea6a33 swift::Parser::parseTopLevel() + 563
17 swift           0x0000000000edb1a0 swift::parseIntoSourceFile(swift::SourceFile&, unsigned int, bool*, swift::SILParserState*, swift::PersistentParserState*, swift::DelayedParsingCallbacks*) + 208
18 swift           0x0000000000cedaa6 swift::CompilerInstance::performSema() + 3254
19 swift           0x00000000008313af
20 swift           0x000000000083046e swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 2702
21 swift           0x00000000007f86fb main + 2747
22 libc.so.6       0x00007fc3dbda8ac0 __libc_start_main + 240
23 swift           0x00000000007f5f49 _start + 41
Stack dump:
0.  Program arguments: /home/rintaro/Documents/swift-oss/build/Ninja-ReleaseAssert/swift-linux-x86_64/bin/swift -frontend -parse -primary-file validation-test/compiler_crashers/28429-swift-decl-print.swift -target x86_64-unknown-linux-gnu -disable-objc-interop -color-diagnostics -module-name main 
1.  With parser at source location: validation-test/compiler_crashers/28429-swift-decl-print.swift:12:1
2.  While walking into decl declaration 0x6db1e30 at validation-test/compiler_crashers/28429-swift-decl-print.swift:10:1
3.  While verifying ranges 'g' at validation-test/compiler_crashers/28429-swift-decl-print.swift:11:1

[slavapestov]

@swift-ci Please smoke test and merge