Cleanup base64::encode functions (#6607)

* Cleanup base64::encode functions

The implementation choice here using libb64 is generally good as it
is a relatively fast implementation, however the adaptation to
use PROGMEM for the translation function was a bad choice, as reading
randomly PROGMEM with byte-wide access is very very very slow.

Doing a naive if-snake is between 20% and 55% faster and uses less
flash (about 120 bytes less) and also for reasons I don't understand
8 bytes less data RAM (maybe the removal of static?).

In addition the base64::encode function was allocating for larger
input a huge amount of memory (twice the total size). we can reduce
that by doing a chunk-wise conversation to base64.

* Create authorisation base64 encoded string without newlines

Rather than first creating a string with newlines and then
stripping it away in the fast path of constructing the query,
we can call the right method and trust that the result does
not have newlines anymore.

libraries/ESP8266HTTPClient/src/ESP8266HTTPClient.cpp

@@ -319,7 +319,7 @@ bool HTTPClient::beginInternal(const String& __url, const char* expectedProtocol
         // auth info
         String auth = host.substring(0, index);
         host.remove(0, index + 1); // remove auth part including @
-        _base64Authorization = base64::encode(auth);
+        _base64Authorization = base64::encode(auth, false /* doNewLines */);
     }
 
     // get port
@@ -504,7 +504,7 @@ void HTTPClient::setAuthorization(const char * user, const char * password)
         String auth = user;
         auth += ':';
         auth += password;
-        _base64Authorization = base64::encode(auth);
+        _base64Authorization = base64::encode(auth, false /* doNewLines */);
     }
 }
 
@@ -516,6 +516,7 @@ void HTTPClient::setAuthorization(const char * auth)
 {
     if(auth) {
         _base64Authorization = auth;
+        _base64Authorization.replace(String('\n'), emptyString);
     }
 }
 
@@ -1243,7 +1244,6 @@ bool HTTPClient::sendHeader(const char * type)
     }
 
     if(_base64Authorization.length()) {
-        _base64Authorization.replace("\n", "");
         header += F("Authorization: Basic ");
         header += _base64Authorization;
         header += "\r\n";