Revise should replace docstring rather than adding to it

[Keno]

38258 added the ability to run doctests with Revise. Unfortunately, this option doesn't seem to actually be working, because Revise adds the new doctest rather than replacing the old one. E.g. here's me trying to work on the jldoctest of getaddrinfo:

julia> (@doc(Sockets.getaddrinfo)).content
2-element Vector{Any}:
 ```julia
getaddrinfo(host::AbstractString, IPAddr) -> IPAddr
```

Gets the first IP address of the `host` of the specified `IPAddr` type. Uses the operating system's underlying getaddrinfo implementation, which may do a DNS lookup.

# Examples

```jldoctest; filter = r"(ip"::1"|ERROR: DNSError:.*|Stacktrace:(\n \[0-9]+\].*)*)
julia> getaddrinfo("localhost", IPv6)
ip"::1"

julia> getaddrinfo("localhost", IPv4)
ip"127.0.0.1"
```

 ```julia
getaddrinfo(host::AbstractString) -> IPAddr
```

Gets the first available IP address of `host`, which may be either an `IPv4` or `IPv6` address. Uses the operating system's underlying getaddrinfo implementation, which may do a DNS lookup.

julia> using Revise

julia> Revise.track(Sockets)

julia> (@doc(Sockets.getaddrinfo))
3-element Vector{Any}:
 ```julia
getaddrinfo(host::AbstractString, IPAddr) -> IPAddr
```

Gets the first IP address of the `host` of the specified `IPAddr` type. Uses the operating system's underlying getaddrinfo implementation, which may do a DNS lookup.

# Examples

```jldoctest; filter = r"(ip"::1"|ERROR: DNSError:.*|Stacktrace:(\n \[0-9]+\].*)*)
julia> getaddrinfo("localhost", IPv6)
ip"::1"

julia> getaddrinfo("localhost", IPv4)
ip"127.0.0.1"
```

 ```julia
getaddrinfo(host::AbstractString) -> IPAddr
```

Gets the first available IP address of `host`, which may be either an `IPv4` or `IPv6` address. Uses the operating system's underlying getaddrinfo implementation, which may do a DNS lookup.

 ```julia
getaddrinfo(host::AbstractString, IPAddr) -> IPAddr
```

Gets the first IP address of the `host` of the specified `IPAddr` type. Uses the operating system's underlying getaddrinfo implementation, which may do a DNS lookup.

# Examples

```jldoctest; filter = r"(ip\"::1\"|ERROR: DNSError:.*|Stacktrace:(\\n \\[0-9]+\\].*)*)"
julia> getaddrinfo("localhost", IPv6)
ip"::1"

julia> getaddrinfo("localhost", IPv4)
ip"127.0.0.1"
```

[Keno]

This might actually be a Base issue. It's using an IdDict for m.docs, but that stores type signatures which do not have a unique objectid unless they're leaf types.

[Keno]

Migrated to Base.