[dev.typeparams] all: merge master (37f9a8f6) into dev.typeparams

Conflicts:

- src/go/types/check_test.go

  CL 330629 fixed a bug in package qualification logic

- src/internal/buildcfg/exp.go

  CL 329930 make parseExperiments get go arch string as input param

Merge List:

+ 2021-06-25 37f9a8f6 go/types: fix a bug in package qualification logic
+ 2021-06-24 c309c89d reflect: document that InterfaceData is a low-entropy RNG
+ 2021-06-24 cce62143 cmd/compile: fix wrong type in SSA generation for OSLICE2ARRPTR
+ 2021-06-24 600a2a4f cmd/go: don't try to add replaced versions that won't be selected
+ 2021-06-24 a9bb3822 net: remove hard-coded timeout in dialClosedPort test helper
+ 2021-06-24 86d72fa2 time: handle invalid UTF-8 byte sequences in quote to prevent panic
+ 2021-06-24 44a12e5f cmd/go: search breadth-first instead of depth-first for test dependency cycles
+ 2021-06-24 73496e0d net: use absDomainName in the Windows lookupPTR test helper
+ 2021-06-24 222ed1b3 os: enable TestFifoEOF on openbsd
+ 2021-06-22 0ebd5a8d cmd/go: update ToolTags based on GOARCH value
+ 2021-06-22 5bd09e5e spec: unsafe.Add/Slice are not permitted in statement context
+ 2021-06-22 666315b4 runtime/internal/atomic: remove incorrect pointer indirection in comment
+ 2021-06-22 63daa774 go/types: guard against checking instantiation when generics is disabled
+ 2021-06-22 197a5ee2 cmd/gofmt: remove stale documentation for the -G flag
+ 2021-06-22 9afd158e go/parser: parse an ast.IndexExpr for a[]
+ 2021-06-21 1bd5a20e cmd/go: add a -go flag to 'go mod graph'
+ 2021-06-21 761edf71 cmd/internal/moddeps: use a temporary directory for GOMODCACHE if needed
+ 2021-06-21 a0400420 cmd/internal/moddeps: use -mod=readonly instead of -mod=mod
+ 2021-06-21 3f9ec83b cmd/go: document GOPPC64 environment variable
+ 2021-06-21 20bdfba3 go/scanner: fall back to next() when encountering 0 bytes in parseIdentifier
+ 2021-06-21 44f9a356 database/sql: fix deadlock test in prepare statement

Change-Id: I16490e8ea70ee65081f467223857033842da513a